Choose the word or set of words that, when inserted in the sentence, best fits the meaning of the sentence as a whole.

The research is so ------- that it leaves no part of the issue unexamined.

A. comprehensive

B. rewarding

C. sporadic

D. economical

E. problematical

正确答案:A

解析:

Try filling in the blank without reading the answer choices. What kinds of words would fit? Words like complete, thorough, or extensive could all fit. Now look at the answer choices. “Comprehensive” is very similar to the words suggested, and none of the other choices fits at all.