问题
单项选择题
It is essential that these application()forms back as early as possible.
A．must be sent
B．will be sent
C．are sent
D．be sent
答案
参考答案：D
解析：
It is essential that…句型要求从句时态用should+动词原形；should常常被省略。这类关键词还有important，best，necessary，important，desirable，advisable，urgent，vital等。故选D。