—Where is my pen?—I it on the desk but I don’t know who it away.A. put; has takenB. put

问题补充：

—Where is my pen?

—I it on the desk, but I don’t know who it away.

A. put; has taken

B. put; took

C. have put; took

D. have put; has taken

答案：

(答案→)A. put; has taken

B. put; took

C. have put; took

D. have put; has taken

解析：考察时态。句意：我的钢笔在哪儿？——我放在桌子上了，但是我不知道谁拿走了它。可知前文叙述的是过去发生的动作，下文强调已经完成的动作，故前文用过去时态，下文用完成时态。Put过去时与原形一样，故选A。