题目内容：

Tiny transmitters(发射机) fixed on the backs of the blue-green bees have allowed scientists to follow the insects as they fly for miles in search of rare flowers．

Working in Panama，scientists caught 17 bees of the common species and fixed a 300 milligram radio light onto the back of each．The signals they sent out were used to follow their movements in and around the forest where they lived．

Professor Martin，from Princeton University，US，and the Max Planck Institute for Ornithology in Germany，said，“By following the radio signals，we discovered that male bees spent most of their time in small centre areas，but could take off and visit areas farther away．One male even crossed over the shipping lanes in the Panama Canal，flying at least 5km，and returned a few days later．”

Researchers have struggled to follow the movements of bees before，following bees marked with paint or using radar which doesn’t work well in forests．

“Carrying the transmitter could reduce the distance that the bees travel，but even if the flight distances we record are the shortest distances that these bees can fly，they are impressive，long-distance movements，” said Dr．Roland Kays，from New York State Museum，a co-author of the research published today in the on-line journal．“This result helps to explain how these bees’ pollination(授粉) can be so rare．” Pollination by bees and other insects is the key to the diversity and continued growth of flowers and trees in some forests．

The new study is the first to use radio transmitters to follow bees in a forest．Similar research may now be carried in temperate forests，where bees also play a vital role．

1.The main purpose of the passage is to___

A． call on people to protect the bees for the environment

B． explain why the bees fly far away in search of flowers

C． introduce a modern way to follow the bees to readers

D． encourage the public to support the scientists' research

2.What was the problem when researchers tried to follow the bees in the past?

A． It was quite difficult to mark the bees

B． The radar itself didn't work very well

C． The bees weren't easy to be recognized

D． Environmental limits were hard to solve

3.What Dr．Roland Kays said implied that____

A． he didn't expect bees could fly so long a distance

B． The transmitter didn't have any effects on bees at all

C． He wanted to know how far bees could travel badly

D． The record was in fact as exact as he had thought

4.Researchers follow the movements of bees mainly to___

A． learn how far they can fly at most

B． discover how they affect the plants

C． correct some wrong ideas about bees

D． get to know where they enjoy living