共用题干 Older Volcanic EruptionsVolcanoes were more destructive in ancient history,not because they were bigger,but because the carbon dioxide they released wiped out life with greater ease.Paul Wignall from the University of Leeds was investigating the link

The policemen acted quickly because lives were at stake.

A:in danger
B:in difficulty
C:in despair
D:out of control

共用题干
Egypt Felled by Famine
Even ancient Egypt's mighty pyramid builders were powerless in the face of the famine that helped bring down their civilization around 2180 BC.Now evidence gleaned（搜集）from mud deposited by the River Nile suggests that a shift in climate thousands of kilometers to the south was ultimately to blame-and the same or worse could happen today.
The ancient Egyptians depended on the Nile's annual floods to irrigate their crops.But any change in climate that pushed the African monsoons（季风）southwards out of Ethiopia would have diminished these floods.
Dwindling（使减少）rains in the Ethiopian highlands would have meant fewer plants to establish the soil.When rain did fall it would have washed large amounts of soil into the Blue Nile and into Egypt,along with sediment（沉积物）from the White Nile.
The Blue Nile mud has a different isotope（同位素）signature from that of the White Nile.So by analyzing isotope differences in mud deposited in the Nile Delta,Michael Krom of Leeds University worked out what proportion of sediment came from each branch of the river.
Krom reasons that during periods of drought,the amount of the Blue Nile mud in the river would be relatively high.He found that one of these periods,from 4,500 to 4,200 years ago,immediately predated the fall of the Egypt's old Kingdom.
The weakened waters would have been catastrophic for the Egyptians."Changes that affect food supply don't have to be very large to have a ripple effect in societies,"says Bill Ryan of the Lamont Doherty Earth Observatory（天文台）in New York.
"Similar events today coald be even more devastating,"says team member Daniel Stanley,a geoarchaeologist from the Smithsonian Institution in Washington, D.0."Anything humans do to shift the climate belts woulld have an even worse effect along the Nile system because the populations have increased dramatically."

Why does the author mention"pyramid builders"?
A:Because they once worked miracles.
B:Because they were well-built.
C:Because they were actually very weak.
D:Because even they were unable to rescue their civilization.

共用题干
第一篇

Plant Gas

Scientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.
Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.
In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.
With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.
Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.
The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.

What was scientists' understanding of methane?
A:It was produced from plants.
B:It was not a greenhouse gas.
C:It was produced in oxygen-free environments.
D:It traps more heat than any other greenhouse gas.

共用题干
Natural Medicines
Since earliest days,humans have used some kinds of medicines.We know this because hu-mans have survived .Ancient treatments for injury and disease were successful enough to keep hu-mans from dying out completely.
They were successful long before the time of modern medicine.Before the time of doctors with white coats and shiny（发亮的）instruments. Before the time of big hospitals with strange and wonderful equipment.
Many parts of the world still do not have university-educated doctors.Nor do they have ex- pensive hospitals.Yet injuries are treated.And diseases are often cured.How?By ancient meth- ods. By medicines that might seem mysterious, even magical（有魔力的）.Traditional medicines are neither mysterious nor magical,however.
Through the centuries, tribal（部落的）medicine men experimented with plants. They found many useful chemicals in the plants.And scientists believe many of these traditional medicines may provide the cure for some of today's most serious diseases.
Experts say almost 80%of the people in the world use plants for health care.These natural medicines are used not just because people have no other form of treatment.They are used be-cause people trust them.In developed areas,few people think about the source of the medicines they buy in a store.Yet many widely-used medicines are from ancient sources,especially plants. Some experts say more than 25%of modern medicines come,in one way or another,from nature.
Scientists have long known that nature is really a chemical factory.All living things contain chemicals that help them survive .So scientists' interest in traditional medicine is not new.But it has become an urgent concern.This is because the earth's supply of natural medicines may be dropping rapidly.

The passage indicates that ancient treatments for injury and disease were_____.
A: much more successful than modern ones
B: successful enough for humans to survive
C: successful in all cases
D: of little help to humans

共用题干
第二篇

Natural Medicines

Since earliest days,humans have used some kinds of medicines.We know this because humans have
survived.Ancient treatments for injury and disease were successful enough to keep humans from dying out
completely.
They were successful long before the time of modern medicine.Before the time of doctors with white
coats and shiny（发亮的）instruments. Before the time of big hospitals with strange and wonderful equipment.
Many parts of the world still do not have university-educated doctors. Nor do they have expensive hospi-
tals.Yet injuries are treated.And diseases are often cured.How?By ancient methods.By medicines that
might seem mysterious , even magical（有魔力的）.Traditional medicines are neither mysterious nor magical,
however.
Through the centuries, tribal（部族的）medicine men experimented with plants. They found many use-
ful chemicals in the plants.And scientists believe many of these traditional medicines may provide the cure
for some of today's most serious diseases.
Experts say almost 80% of the people in the world use plants for health care.These natural medicines
are used not just because people have no other form of treatment.They are used because people trust them.
In developed areas,few people think about the source of the medicines they buy in a store.Yet many wide-
ly-used medicines are from ancient sources,especially plants.Some experts say more than 25% of modern
medicines come,in one way or another,from nature.
Scientists have long known that nature is really a chemical factory.All living things contain chemicals
that help them survive.So scientists' interest in traditional medicine is not new.But it has become an ur-
gent concern.This is because the earth's supply of natural medicines may be dropping rapidly.

The passage indicates that ancient treatments for injury and disease were_________.
A:much more successful than modern ones
B:successful enough for humans to survive
C:successful in all cases
D:of little help to humans

共用题干
Older Volcanic Eruptions
Volcanoes were more destructive in ancient history,not because they were bigger,but because the carbon dioxide they released wiped out life with greater ease.
Paul Wignall from the University of Leeds was investigating the link between volcanic eruptions and mass extinctions.Not all volcanic eruptions killed off large numbers of animals,but all the mass extinctions over the past 300 million years coincided with huge formations of volcanic rock.To his surprise,the older the massive.volcanic eruptions were,the more damage they seemed to do.He calculated the"killing efficiency" for these volcanoes by comparing the proportion of life they killed off with the volume of lava（熔岩）that they produced.He found that size for size,older eruptions were at least 10 times as effective at wiping out life as their more recent rivals.
The Permian（二叠纪）extinction,for example,which happened 250 million years ago,is marked by floods of volcanic rock in Siberia that cover an area roughly the size of western Europe.Those volcanoes are thought to have pumped out about 1 0 gigatonnes（十亿吨）of carbon as carbon dioxide.The global warming that followed wiped out 80 percent of all marine genera（种类）at the time,and it took 5 million years for the planet to recover.Yet 60 million years ago,there was another huge amount of volcanic activity and global warming but no mass extinction.Some animals did disappear but things returned to normal within ten thousands of years."The most recent ones hardly have an effect at all,"Wignall says.He ignored the extinction which wiped out the dinosaurs 65 million years ago,because many scientists believe it was primarily caused by the impact of an asteroid（小行星）.He thinks that older volcanoes had more killing power because more recent life forms were better adapted to dealing with increased levels of CO₂.
Vincent Courtillot,director of the Paris Geophysical InstitUte in France,says that Wignall's idea is provoca- tive.But he says it is incredibly hard to do these sorts of calculations.He points out that the killing power of volcanic eruptions depends on how long they lasted.And it is impossible to tell whether the huge blasts lasted for thousands or millions of years.He also adds that it is difficult to estimate how much lava prehistoric volcanoes produced,and that lava volume may not necessarily correspond to carbon dioxide emissions.

Which of the following is wrong according to Paragraph 3?
A:Only 80 percent of marine genera survived the global warming caused by the Permian extinction.
B:It took 5 million years for the planet to recover from the Permian extinction.
C:The huge amount of volcanic activity and乡obal warming 60 million years ago did not lead to mass extinction.
D:The cause of dinosaurs'extinction has remained a controversial issue.

The firemen acted quickly because lives were at stake.

A:in danger
B:in despair
C:out of condition
D:out of danger

共用题干
第一篇

Plant Gas

Scientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.
Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.
In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.
With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.
Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.
The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.

Which statement is true of the methane emissions of plants in the experiment?
A:The lower the temperature,the higher the amount of methane emissions.
B:Living plants release less methane than dried plants at the same temperature.
C:When exposed to sunlight,plants stop releasing methane.
D:The higher the temperature,the greater the amount of methane emissions.