By the end of last month I all the CDs of Justin Bieber.A. collectB. collectedC. have co

问题补充：

By the end of last month, I all the CDs of Justin Bieber.

A. collect

B. collected

C. have collected

D. had collected

答案：

A. collect

B. collected

C. have collected

(答案→)D. had collected

解析：考查点：过去完成时的用法。 解题思路：此处by意为“到…为止”，该句意为“到上个月末为止，我已经将Justin Bieber全部的CD收集起来”，表示“动作从过去已经开始一直持续到过去某个时间”，故要使用过去完成时，答案选D；