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

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(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。