By the time I was five I learning English.A. had startedB. have startedC. startedD. have

问题补充：

By the time I was five, I learning English.

A. had started

B. have started

C. started

D. have been

答案：

(答案→)A. had started

B. have started

C. started

D. have been

解析：根据题意可知，开始学英语是在我我五岁之前，所以应该用过去完成时，故排除BCD。本句的意思是“当我五岁的时候，我开始学英语。”所以本题选A。