—What were you up to when she dropped in?—I for a while and some reading.A. was playing;

问题补充：

—What were you up to when she dropped in?

—I for a while and some reading.

A. was playing; was going to do

B. played; did

C. had played; was going to do

D. had played; did

答案：

A. was playing; was going to do

B. played; did

(答案→)C. had played; was going to do

D. had played; did

解析：由第一句可判断出第二句描述的事情发生在过去，for a while是相对于when she dropped in来说的when she dropped in，“我已经玩一会儿了”，因此该用过去完成时态．再看后一个动作，承接前面for a while，仍然在过去，had played for a while之后，因此应用过去将来时，表示过去那个时间将要发生的动作，故选C。