Hes been collecting stamps _he was eight years old.A. whenB. whileC. andD. since

问题补充：

Hes been collecting stamps _he was eight years old.

A. when

B. while

C. and

D. since

答案：

A. when

B. while

C. and

(答案→)D. since

解析：句意：自从他八岁时，他已经开始收集邮票。分析主句是现在完成时，从句是时间，因此只有since符合题意。故选 D