The policeman checked the room carefully to _______ nobody was in.

A. cut down B. write down C. make sure D. take up

C

句意“这个警察仔细检查房间确保没人在里面”。A.削减；B.写下；C.确保；D.占据。根据句意可知，表示“确保里面没人”，故选C。