e roughly the same intelligence.

答案C，主旨大意题。本文一共两段，第一段写了出生和环境对人的智商都有影响，第二段举例说明环境对智力发展的影响，所以最符合文章大意的是C选项。

12. According to the passage, the average I. Q. is_____

A. 85 

B.100 

C. 110 

D. 125

答案B，细节题，关键词是average，第二段最后一句话 “Mark’s I. Q. was 125, twenty-five points higher than the average”，可以看出，平均智商是125-25=100。

13. The case history of twins appears to support the conclusion that _____.

A. individuals with identical brains are seldom tested

B. an individual's intelligence is determined only by his environment

C. lack of educational opportunities blocks the growth of intelligence

D. changes of environment produce changes in the structure of the brain

答案C，第二段举例说明环境也就是教育对智力发展的影响。

14. This passage suggests that an individual's I. Q.______ . 

A. can be predicted at birth

B. stays the same throughout his life

C. can be increased by education

D. is determined by his childhood

答案C，第二段举例说明环境也就是教育对智力发展的影响，也就是通过接受教育可以增加智力。

15. The best title of this passage is _____

A. M