Scientists who study insects (昆虫)are troubled now.All across the United States，bees are leaving their hives(蜂箱)and never returning.According to the beekeepers across the country,25 to 40 percent of the bees in the United States have left their hives since last fall.So far，no one can explain why.
Bees play an important role in the production of about one third of the food we eat.A large number of plants not only need people's care but also need bees that spread pollen (花粉)from flower to flower.Without this_process，a plant can't produce seeds or fruits.
Now，a group of scientists and beekeepers are trying to find out what has happened.By examining bees' behavior and health，they hope to find out what has caused the bees' disappearance and to prevent bees from disappearing in the future.
Some people think the disappearance may be caused by disease.According to Dewey Caron，a researcher at the University of Delaware，the bees have signs of troubled immune systems (免疫系统)inside their bodies.But why would troubled immune systems cause bees to leave their hives？After all，when people are sick，they want to stay at home.Caron guesses that sick bees may have difficulty figuring out where their homes are.
“Another cause may be some chemicals (化学药品)that farmers use to kill unwanted insects on crops.” says Jerry Hayes，who works at the Florida Department of Agriculture.
5．The underlined part“this process” refers to ________.
A．people's care
B．bees' leaving their hives
C．bees' spreading pollen from flower to flower
D．beekeepers' raising bees
6．It can be inferred from the passage that ________.
A．the use of some chemicals is the cause of the bees disappearance
B．sick bees are not able to find where their hives are
C．it's not known yet why a lot of bees are leaving their hives and never returning
D．there will be no bees in America in the near future
7．What would be the best title for the passage?
A．Bees，Humans' Friends
B．Scientists Are Interested in Bees
C．Why Are Bees Leaving?
D．How Do Bees Send out Information?
8．The passage is most probably taken from ________.
A．science news
B．a public advertisement
C．a book on advanced technology
D．a business report