---Where is my reference book? It was here a moment ago.---Someone it by mistake.A. could

问题补充：

---Where is my reference book? It was here a moment ago.---Someone it by mistake.

A. could have taken

B. must take

C. might take

D. must have taken

答案：

A. could have taken

B. must take

C. might take

(答案→)D. must have taken

解析：在肯定句中对过去发生的事情的推测要用must have done。这里表示肯定有人错拿了。