为什么选 be sent must be sent 不行?He promised me that the messagea__be sent__at once.He promised me that the messagea_________at once.A) could be sent\x05\x05B) would be sentC) must be sent\x05\x05D) be sent我觉得 A B C 为什么选D?

为什么选 be sent must be sent 不行?He promised me that the messagea__be sent__at once.He promised me that the messagea_________at once.A) could be sent\x05\x05B) would be sentC) must be sent\x05\x05D) be sent我觉得 A B C 为什么选D?
为什么选 be sent must be sent 不行?He promised me that the messagea__be sent__at once.
He promised me that the messagea_________at once.
A) could be sent\x05\x05B) would be sent
C) must be sent\x05\x05D) be sent
我觉得 A B C 为什么选D?

为什么选 be sent must be sent 不行?He promised me that the messagea__be sent__at once.He promised me that the messagea_________at once.A) could be sent\x05\x05B) would be sentC) must be sent\x05\x05D) be sent我觉得 A B C 为什么选D?
promise引导的从句其实是有省略一个should的,所以说ABC都不行,