有机物反应活性（organic reactivity）

活性污泥法中的需氧量计算需要考虑( )。

A、有机物氧化需氧量和活性污泥自身氧化需氧量
B、有机物氧化需氧量和混合液表面散氧量
C、有机物氧化需氧量和剩余污泥消化需氧量
D、延时曝气活性污泥法中只需考虑有机物氧化需氧量

共用题干
Organic Food:Why?

1 Europe is now the biggest market for organic food in the world,expanding by 25 percent a year over
the past 10 years.So what is the attraction of organic food for some people?The really important thing is
that organic sounds more"natural".Eating organic is a way of defining oneself as natural,good,caring,
different from the junk-food-eating masses.
2 Unlike conventional farming,the organic approach means farming with natural,rather than man-
made , fertilisers and pesticides. Techniques such as crop rotation（轮种）improve soil quality and help
organic farmers compensate for the absence of man-made chemicals.As a method of food production,organic
is,however,inefficient in its use of labour and land;there are severe limits to how much food can be pro-
duced.Also,the environmental benefits of not using artificial fertilisers are tiny compared with the amount of
carbon dioxide emitted（排放）by transporting food.
3 Organic farming is often claimed to be safer than conventional farming. Yet studies into organic
farming worldwide continue to reject this claim.An extensive review by the UK Food Standards Agency found
that there was no statistically significant difference between organic and conventional crops.Even where re-
sults indicated there was evidence of a difference,the reviewers found no sign that these differences would
have any noticeable effect on health.
4 The simplistic claim that organic food is more nutritious than conventional food was always likely to
be misleading. Food is a natural product,and the health value of different foods will vary for a number of rea-
sons,including freshness,the way the food is cooked,the type of soil it is grown in,the amount of sunlight
and rain crops have received,and so'on.Likewise,the flavour of a carrot has less to do with whether it was
fertilised with manure（粪便）or something out of a plastic sack than with the variety of carrot and how long
ago it was dug up.
5 The notion that organic food is safer than"normal"food is also contradicted by the fact that many of
our most common foods are full of natural toxins（毒素）.As one research expert says: "People think that the
more natural something is,the better it is for them.That is simply not the case.In fact,it is the opposite
that is true:the closer a plant is to its natural state,the more likely it is that it will poison you.Naturally,
many plants do not want to be eaten,so we have spent 10,000 years developing agriculture and breeding out
harmful traits from crops."

Paragraph 1_______
A:Factors That Affect Food Health Value
B:Main Reason for the Popularity of Organic Food
C:Testing the Taste of Organic Food
D:Research Into Whether Organic Food is Better
E:Necessity to Remove Hidden Dangers From Food
F:Description of Organic Farming