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

问题补充：

By the end of the 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：这里是考核时态的内容，根据by the end of+过去时间，我们知道是考核“过去完成时”的内容。