——Susan stays alone in the classroom and looks sad ——______to her?A,What happens?B.What has happened?C.What is happening?D.What was happening?

——Susan stays alone in the classroom and looks sad ——______to her?A,What happens?B.What has happened?C.What is happening?D.What was happening?
——Susan stays alone in the classroom and looks sad ——______to her?
A,What happens?
B.What has happened?
C.What is happening?
D.What was happening?

——Susan stays alone in the classroom and looks sad ——______to her?A,What happens?B.What has happened?C.What is happening?D.What was happening?
B
现在完成时,“她发生了什么事”,这件事已经发生并且已经结束
A选项是一般现在时,不符合已经发生的题意
C选项是现在进行时,表示正在进行,也不符合已经发生的题意
D选项是过去进行时,即过去正在进行,很明显这件事情已经发生了,而不是过去正在发生