2． What was scientists’ understanding of cryptic species?
A They occurred in equal numbers in all biogeographical regions．
B They were mostly found in insects find reptiles．
C They were likely to be in tropical rather than temperate regions．
D Both B and C．
3． Do scientists know how many cryptic species exist?
A Not yet．
B Yes，they do．
C They will know the answer in another one or two years;
D They will never know the answer．
4． Which of the following about the African bush elephant and the African elephant is true?
A The WCU are interbreeding those elephants．
B They are interbreeding species．
C They are two genetically distant species．
D They depend on each other for survival．
5． People were confused in their attempts to control malaria in Europe in the early1900s，because scientists
A identified only one mosquito species instead of six species．
B thought only three mosquito species transmitted disease．
C thought there was only one mosquito species．
D did not know what species was being studied．
答案与题解：
1． D 短文的第一段第二句的大意是，研究结果为广泛的研究领域提供启示，包括生物多样性研究，还能帮助我们理解传染疾病及其演变。所以，选项A、B、C都是正确的，它们不是答案。选项D的“适者生存”的内容文章中没有提及，因此是本题的答案。
2． D 短文的第二段第二句描述的是科学家目前的研究结果，第三段描述的是科学家在这之前对于cryptic species的理解。本题用的是过去式，问的是过去的状况，因此，答案在第三段中，B和C是答案，所以D是正确选择。
3． A 第三段和第五段提供了答案。第三段的倒数第二句中的Until．．．no one will know just how many cryptic species exist．其意思就是人们目前还不了解。第五段的最后一句也说明了研究者目前对此尚未了解。
4． C 答案在第六段中。该段举了非洲大象为例，说明什么是cryptic species.第六段的句子“A 2001 study found the elephants were actually two genetically distinct，non- interbreeding spemes”是选择C的依据。选项A不对，the WCU并没有杂交繁殖这两种象。选项B不对，短文说这两种象是非杂交物种。选项D的内容短文中找不到。
5． A 短文最后一段告诉我们，由于对蚊子种类不了解，20世纪初期疟疾曾肆虐欧洲，最终，科学家才了解到蚊子这一物种不是由一个种类而是由六个种类组成。所以，应该选择A.