【题目】 It was essential that the application forms ___________ back before the deadline .
A. must be sent B. would be sent
C. be sent D. were sent
在线课程【答案】C
【解析】
试题分析：考查虚拟语气。形容词essential和necessary通常和虚拟语气连用，虚拟语气的结构为“should+动词原形”，其中should可以省略。句意：申请表必须在最后期限之前发回来。根据句意可知使用被动语态，C项中省略了should。故C正确。