means of transport for auxin...可知， PILS proteins在生长素的传播过程中起着至关重要的作用。

　　【答案】　D

　　3．According to Paragraph 2，the researchers got their results mainly by ．

　　A．referring to Darwin's theory

　　B．observing plants straightening

　　C．doing intensive molecular research

　　D．watching plants in different places

　　【解析】　细节理解题。达尔文一开始只是对生长现象感兴趣但并没有得出结论，只有现在的研究者经过了"密集的分子生物学研究"之后才得出结论。

　　【答案】　C

　　4．Which of the following can be the BEST title for this passage?

　　A．Why Plants Grow towards the Light?

　　B．Darwin's Dream Has Come True

　　C．How Did Scientists Find Out the Secret?

　　D．A New Way of the Growing of Plants

　　【解析】　标题归纳题。文章一开始就以疑问的方式提出了主题，然后陆续揭示auxin的功能。

　　【答案】　A

　　B

　　Humans aren't the only ones getting a buzz from coffee. Caffeine can improve memory among honeybees and lead to better pollination(授粉). According to a recent study published in the journal Science.

The study was conducted by a team of researchers at Newcastle University in the United Kingdom. They found that the nectar(花蜜)of some flowers, such as those from grapefruit and lemon plants, as well as certain coffee flowers, contains low doses of caffeine. To get bees to feed on these flowers, the team trained the insects to associate food with the smell of the flowers. They also trained another group of bees to feed on nectar from flowers that were sweetened with a sugar, but did not contain