Researchers found that caffeine’s effect on the bee brain is similar to its effect on mammals．“The change is similar to that produced by caffeine in neurons(神经元)associated with learning and memory in the rat brain，”Wright said．
Bee populations have declining since 2007．The dramatic drop in the insects’numbers has serious effects for ecosystems and the farming industry．Bees are needed in the reproduction of crops and spreading wild flower species．Understanding what keeps bees buzzing could help to make sure that the insects are able to remember and pollinate their favorite flowers．
21．Which of the following is mentioned in the passage?
A．Caffeine has no effect on the rat brain． B. Bee population has been increasing．
C．The nectar of lemon plants contains caffeine． D．Bees dislike nectar from sweetened flowers．
