When I entered the classroom I saw the students in their seats. A. sitting B. are sitti

问题补充：

When I entered the classroom, I saw the students in their seats.

A. sitting

B. are sitting

C. sat

D. to sit

答案：

A. sitting

B. are sitting

C. sat

D. to sit

解析：考查宾语补足语用法。See sb do sth看见某人做了某事（事情的全过程）；see sb doing sth看见某人正在做某事（动作正在发生）。句意：当我进入教室的时候，我看见学生们正坐在他们的位置上。