—You may find the key to the math problem on page 107．
—Ah, it's so simple． I wonder why I _ of that．
A. hadn't thought
B. haven't thought
C. didn't think
D. wasn't thinking
网友回答
A. hadn't thought
B. haven't thought
(答案→)C. didn't think
D. wasn't thinking
解析：考查时态：句意：--你可以在107页找到数学问题的答案。--哦，是这么简单，我当时没想到这句应该用过去式，A表示过去的过去B表示到现在没想到，D是过去没有在想。选C。