Mary decided not to work on the program at home because she didn’t want her parents to kno

问题补充：

Mary decided not to work on the program at home because she didn’t want her parents to know what she .

A. has done

B. had done

C. was doing

D. is doing

答案：

A. has done

B. had done

(答案→)C. was doing

D. is doing

解析：考查时态。句意：Mary决定不在家里做那个项目，因为她不想她的父母知道她正在做的事情。根据句子的decided说明本句的基本时态是过去时，根据句意说明是过去的那段时间正在做的事情，故使用过去进行时。故C正确。