― Have you finished your composition already Jack?― Yes. I it within half an hour.A. hav

问题补充：

― Have you finished your composition already, Jack?

― Yes. I it within half an hour.

A. have finished

B. finish

C. finished

D. will finish

答案：

A. have finished

B. finish

(答案→)C. finished

D. will finish

解析：句意：―杰克，你写完你的作文了吗？― 是的，我半个小时就完成了。C. finished为一般过去时，一般过去时也可以表示过去一段时间内发生的动作。A. have finished是现在完成时;B. finish是一般现在时; D. will finish 是一般将来时的谓语动词形式。