John in his room when he heard screaming.A. is studyingB. studiedC. was studyingD. has st

问题补充：

John in his room when he heard screaming.

A. is studying

B. studied

C. was studying

D. has studied

答案：

A. is studying

B. studied

(答案→)C. was studying

D. has studied

解析：重点理解句意，从而判断时态的选择。句意：当约翰听见尖叫声时，他正在他的房子里学习。从when所引导的时间状语从句看，动作发生在过去，可知句子要用过去进行时，表示过去某个时间正在做某事。