What were you doing this time yesterday?　　I on the grass and drawing a picture.A.

问题补充：

--- What were you doing this time yesterday?

--- I on the grass and drawing a picture.

A. sit

B. sat

C. am sitting

D. was sitting

答案：

A. sit

B. sat

C. am sitting

(答案→)D. was sitting

解析：本题是对动词时态的考察，问句和答句时态上要统一，问句是过去进行时，对于过去的某一时间的动作提问，所以答句使用过去进行时。