-- Did you visit your grandparents yesterday?--Yes and when I got there they in the fie

问题补充：

-- Did you visit your grandparents yesterday?

--Yes, and when I got there, they in the fields .

A. worked

B. have worked

C. were working

D. had worked

答案：

A. worked

B. have worked

(答案→)C. were working

D. had worked

解析：句意：--昨天你去看祖父母了吗？--是的，当我到达那里的时候，他们正在田里干活。时间状语是when I got there,说明是在过去某个时间正在做…，符合过去进行时的用法，选C。