2. Which of the following best interprets the meaning of “While the chimps worked out ” （the first sentence of the third paragraph）？
A While the chimps worked in the lab
B While the chimps exercised in the gym
C While the chimps tried to figure out what they should do
D While the chimps tried to understand the instructions
3. What was the result of the finding，according to Paragraph 5？
A Three chimps used more energy walking on two legs.
B One chimp used less energy walking on two legs.
C One chimp used about the same energy walking on two legs as on four.
D All of the above.
4. What was true of the hypothesis of the research？
A Our apelike ancestors were anatomically different but had the same gaits.
B Bipeds with natural selection had an advantage over quadruped.
C Our apelike ancestors could adapt to different climate changes due to genetic variation.
D Bipeds had an advantage over quadrupeds due to changes in the environment.
5. What does fossil and molecular evidence tell us about our earliest ancestors？
A They experienced more climate changes than we do today.
B Due to changes in climate，they were forced to travel between food patches.
C They could cover more ground than their quadrupedal peers because they used less energy.
D They could travel longer distances on the ground than those who could use less energy.
答案与题解：
1. C 短文的第一段直接回答了这个问题。
2. B worked out在此是“运动，锻炼”的意思，所以选择B.
3. D 第五段的第三、第四和第五句提供了答案。bipedalism was more expensive的意思是：两足行走消耗更多的体能。walking upright的意思是：直立行走，即两足行走。
4. B 第六段告诉了我们研究的两个假设：猿人祖先在解剖学意义上存在着差异，这一差异影响了它们的步态；这些差异在自然选择的过程中决定了遗传变异，而环境变化使得两足行走的猿人比起四足行走的猿人更有战势。A、C、D都不是正确的说法，只有B在该段中被提到。
5. C 倒数第二段提供了问题的答案。travel longer distances用的是比较级，这里是将两足行走的猿人与上文中四足行走的猿人做比较。those who could cover more ground using less energy指的是上文提到的与四足行走的猿人相比，体能消耗较小的两足行走猿人。其他选择都不是正确说法。