.Your son has kept for two hours. You’d better ask him to have a rest.A. studyB. studiedC

问题补充：

.Your son has kept for two hours. You’d better ask him to have a rest.

A. study

B. studied

C. to study

Dstudying

答案：

A. study

B. studied

C. to study

(答案→)D. studying

解析：keep doing保持不间断地做某事

keep to do keep要求 -ing, 没有 to do 形式

故选D.