问题补充:
The message is very important, so it is supposedas soon as possible.
A. to be sent
B. to send
C. being sent
D. sending
答案:
(答案→)A. to be sent
B. to send
C. being sent
D. sending
解析: be supposed to do是固定搭配。又因it(the message)与send因为被动关系,故用动词不定式的被动语态。