单选题There are（）rats on board.A notB noC anyD none

共用题干
第二篇

Exercise and Brain

Just as exercise strengthens the heart and lungs,bones and muscles,it may also power up the brain.A succession of scientific studies of animals implies that physical activity has a positive effect on mental functioning.
"It's clear that the brain benefits from exercise,"says brain scientist William Greenough of the University of Illinois at Urbana-Champaign.His studies with rats have demonstrated two primary effects of activity:Vigorous physical exercise provides the brain with more fuel,and skill-based ex-ercise increases the formation of connections in the brain, which, according to the proposals of some scientists,may make the brain better able to process information.
In one experiment,laboratory rats were separated into three groups.One group was exercised by running inside an automatic wheel,a second group improved their skills in a complicated obstacle course,and a third group was inactive.
"The animals that learned to go through the obstacle course exhibited a greater number of brain connections than the animals in the exercised or inactive groups,"Greenough said."In contrast, the animals that exercised inside the automatic wheel possessed a greater density of blood vessels in the brain than did either of the other two groups of animals."
Learning a new dance step may boost the brain in the same way that learning a language can, he says.And if the dance is a good physical exercise as well,the benefits multiply.Young brains may be especially able to boost brain power through exercise,suggested another of Greenough's experiments that showed the most significant changes in the brain occurred among rats that had been exercised when very young.And while animals aren't people,he says it is logical to make the inference that an effect found in rats may also apply to humans.
Human studies have focused primarily on older adults and suggest that regular exercise can improve the speed with which the brain processes information.Measurements made by Arthur Kramer at the University of Illinois demonstrated that inactive adults,aged 63 to 82,could hit buttons faster in response to a tone after they went through a 10-week water exercise course.A corresponding control group that didn't exercise showed no improvement.

Which statement is correct according to the passage?
A:The effect of exercises found in rats can not apply to people.
B:Changes in the brain occurred among young rats are more significant than those among adult rats.
C:Regular exercise can only improve the speed with which the older adults' brain processes information.
D:The author encourages people do more skill-based exercise instead of vigorous physical exercise.

共用题干
Are You Getting Enough Sleep?

What happens if you don't get enough sleep? Randy Gardner,a high school student in the United
States,wanted to find out. He designed an experiment on the effects of sleeplessness for a school science
project. With doctors watching him carefully,Gardner stayed awake for 264 hours and 12 minutes.That's
eleven days and nights without sleep!
What effect did sleeplessness have on Gardner? After 24 hours without sleep,Gardner started having
trouble reading and watching television. The words and pictures were too blurry（模糊）.By the third day,
he was having trouble doing things with
his hands. By the fourth day, Gardner was hallucinating（产生幻
觉）.For example,when he saw a street sign,he thought it was a person.He also imagined he was a famous
football player. Over the next few days, Gardner's speech became so slurred（不清楚）that people couldn't
understand him.He also had trouble remembering things.By the eleventh day, Gardner couldn't pass a
counting test.In the middle of the test he simply stopped counting.He couldn't remember what he
was doing.
When Gardner finally went to bed,he slept for 14 hours and 45 minutes.The second night he slept for
twelve hours,the third night he slept for ten and one-half hours,and by the fourth night,he had returned to
his normal sleep schedule.
Even though Gardner recovered quickly,scientists believe that going without sleep can be dangerous.
They say that people should not repeat Randy's experiment. Tests on white rats have shown how serious
sleeplessness can be. After a few weeks without sleep, the rats started losing their fur（皮毛）.And even
though the rats ate more food than usual,they lost weight.Eventually the rats died.
During your lifetime,you will probably spend 25 years or more sleeping.But why?What is the purpose
of sleep? Surprisingly,scientists don't know for sure.Some scientists think we sleep in order to
replenish（补充）brain cells. Other scientists think that sleep helps the body to grow and to relieve stress.
Whatever the reason,we know that it is important to get enough sleep.

Going without sleep is not dangerous for white rats.
A:Right
B:Wrong
C:Not mentioned

共用题干
第三篇

Sugar Accelerate the Process of Aging

Sugar is widely used in our daily life to make food and drinks sweet,though too much intake of it may lead to diabetes.However,today's study found it also makes people get old faster. Rats that eat high levels of a natural sugar known as fructose seem to age faster than other rats.And the same could be true for people who eat too much sweet junk food,said Israeli researchers.
Fructose,a substance found naturally in honey and fruit,is used widely in foods ranging from soft drinks to yogurt. But while its sweet taste is popular,the sugar could cause wrinkles and health problems,the researchers said.Dr. Moshe Werman and Boaz Levi of the Technion-Israel Institute of Technology fed large amounts of fructose to laboratory rats.Writing in the Journal of Nutrition,they said the fructose-fed rats showed changes in the collagen of their skin and bones.
Collagen,a fibrous protein found in connective tissue,bone and cartilage,basically holds the body together. The loss of collagen is what causes sagging and deep wrinkles in older people.
The process affected,Werman's team said,is known as"cross linking"."Too much crosslinking reduces elasticity and makes the skin stiff and rigid,and these are the conditions that encourage wrinkled skin,"Werman said in a statement. He said the same could be true of people, although this has not been shown."Americans are eating more and more processed foods such as carbonated drinks,baked goods,canned fruits,jams and dairy products that contain fructose," Werman said.Other studies have shown that high fructose intake can affect how the body handles glucose and increases insulin resistance一which can both be important measures of the tendency toward diabetes.
The rats Werman worked with were fed much more than the average adult person might eat in a day,which is standard in such experiments.The rats were 12.5 grams of fructose per kg(2.2 pounds)of weight every day for a year. To compare,a person weighing 154 pounds(70kg)who drinks a quart(liter)of cola consumes about 60 grams of fructose,or 0.8 grams per kg of body weight.

According to the passage,people who eat too much sweet junk food will_______.
A:slow down their process of aging
B:more likely to get diabetes
C:get heavier than others
D:age faster than average people