It is strange that the small boy work out such a difficult exercise, which is even hard to settle for adults.
A. should
B. might
C. could
D. would
网友回答
A. should
B. might
C. could
(答案→)D. would
解析：情态动词辨析。A. 应该 B.可能 C.能够；can的过去时态 D.将要。句意：很奇怪，这个小男孩想要算出如此难的一道，甚至成年人都很难解决的练习。选D。