1. The line of descent of apes and humans is believed by most paleontologists (that it split) into several branches some time between 20 million and 5 million years ago
A. that it split
B. to have split
C. to split
D that they were split
E to be split
answer B, 为什么样 C 不行? 不定式用完成时态表过去发生的事情吗?
2. Alcohol may interfere with the abilitty of the brain cells (as they form) the proteins considered essential to short-term memory.
A. as they form
B. forming
C. in the formation of
D to form
E when they form
answer D, 我觉得应该是A. as 表原因.
3. The Census Bureau reports that more than three-fifths of all married couples in the United States now have two incomes, significantly more than (earlier decades did).
A earlier decades did
B earlier decades
C in earlier decades
D earlier decades have
E that in earlier decades
