D.they were often ill and they couldn't play with their children

答案:B

解析:根据第五段中的"...64% said they were often too tired to play with them."可知选B项。

3.What does the passage mainly talk about?

A.The health service in the UK.

B.A study of British people's lifestyles.

C.A study of British people's laziness.

D.The fatness problem in the UK.

答案:C

解析:根据第二段中的"A study into how lazy British people are has found..."可知选C项。

　　It happens every spring.Flowers come out everywhere on the same day.But how do plants"know" when to flower?

　　For years,it has been a difficult question for scientists.But a US research group may have finally answered it-the secret lies in a protein (蛋白质) called FKF1.This helps plants to know when the days become long and when they get short.Then they can tell the seasons are changing.

　　Researchers found the FKF1 protein when they were studying a plant called Arabidopsis (拟南芥).It is sensitive (敏感的)to sunlight,and can be made active by sunlight.

　　Plants produce this protein every day in the late afternoon all year.If there is no light at this time,for example in winter when the sun goes down early,the protein won't be active.But when spring comes and the days get longer,the FKF1 protein can be made active by day light and the plants "know" it is time to flower."If there is light in the late afternoon,plants will know that the days are getting longer and that it is the best time for flowers to come out," explained Takato Imaizumi,leader of the study.But when conditions are poor for growing,such as during autumn or winter when the weather is cold and days are short,plants won't flower.

　　Although researchers have only studied how the FKF1 protein works in the Arabidopsis,they believe that it is the same with many other plants,including crops such as rice and wheat.This could be useful to the agricultural industry.

　　"If we can control when flowers come out,we might be able to increase crop production," Imaizumi said.

4.The passage is mainly about 　　　.

A.how plants"know" when to flower　

B.what people can do with plants

C.how seasons are changing　

D.what kind of plant Arabidopsis is

答案:A

解析:本文在第一段开篇点题"But how do plants 'know' when to flower?",其后围绕这个话题展开论述,因此选A项。