答案　C

解析　细节理解题。根据第四段第二句可知，私人晚宴过后，兰斯特和莫兰会让客人向慈善机构捐款。

19．Which of the following words can best describe Lanster and Moran?

A．Ambitious. B．Generous.

C．Creative. D．Optimistic.

答案　B

解析　推理判断题。根据第三段最后一句"After their last 12­person event，Lanster and Moran gave1,600 to the charity."可知，两个年轻人通过举办私人晚宴，迄今为止已经向这家慈善机构捐赠了1600美元。由此可推出，这两个孩子是非常慷慨的。

　　话题：自然　难度星级：☆☆☆

　　Scientists have identified the order of the gene of the giraffe for the first time to help explain how the tallest animals on earth developed their remarkably long necks.

　　Being a giraffe is not easy. To pump blood two meters up from the chest to the brain calls for a powerful heart and twice the blood pressure of other mammals. Giraffes also need special safety system to let them bend down for a drink and raise their heads again without feeling dizzy.

　　The animals' unique body structure has long been a puzzle for biologists，including Charles Darwin. Now，by comparing the gene of the giraffe with that of its closest relative，the short­necked okapi，scientists have solved part of the puzzle by studying changes in a small number of genes responsible both for regulating body shape and circulation. This suggests that the development of a long neck and a powerful heart went hand in hand，driven by a relatively small number of genetic changes.

　　The interpretation of the genetic factors behind the giraffe's remarkable heart system could also be instructive for human health，since the animals appear to avoid the kind of organ damage often found in people with high blood pressure.

　　The more fundamental question of why giraffes developed their long necks remains open，however. The apparently self­evident idea that it was to reach ever­higher food supplies has been challenged in the past 20 years by a competing belief that it is actually due to competition among fighting males for females.

　　Unlike long­necked birds，which have additional vertebrae(椎骨)，giraffes have the same seven vertebrae found in all mammals，although theirs are greatly extended.

语篇解读　本文讲述了科学家第一次确定了长颈鹿的基因序列，由此明白了长颈鹿进化出长脖子的原因。