-----Tom. You look very bored and tired.-----Yes I my father on the farm until seven o’c

问题补充：

-----Tom. You look very bored and tired.

-----Yes, I my father on the farm until seven o’clock this morning.

A. have been helping

B. had helped

C. was helping

D. am helping

答案：

A. have been helping

B. had helped

(答案→)C. was helping

D. am helping

解析：由表示过去的时间状语until seven o’clock this morning可知, 前面用过去进行时。本题注意不要受思维定势的影响而用现在完成进行时，要深入体会动作的时间性。