They______ when the teacher came in.

They______ when the teacher came in.

A．talk              B．are talking         C．to talk            D．were talking

They______ when the teacher came in.

1. A.
   talk
2. B.
   are talking
3. C.
   to talk
4. D.
   were talking

句型转换

They were talking when their teacher came in. (对画线部分提问)

________ ________ they ________ when the teacher came in?