Students are supposed hard at school.A. studyingB. studiedC. to studyD. study

问题补充：

Students are supposed hard at school.

A. studying

B. studied

C. to study

D. study

答案：

A. studying

B. studied

(答案→)C. to study

D. study

解析：考查短语be supposed to do sth 应该做某事，被期望做某事。句意：学生们应该在校努力学习。选C。