There was something wrong with the network，or the e-mail earlier.
A. could have been sent
B. might be sent
C. need have been sent
D. must be sent
网友回答
(答案→)A. could have been sent
B. might be sent
C. need have been sent
D. must be sent
解析：
试题分析:考查情态动词的用法。A可能已经被发送； B 或许要被发送 C 过去需要被发送；D 肯定要被发送；句意：网络出故障了，否则这个邮件早就被发送出去了。从句子时态可以判断是对过去的推测，情态动词+动词原形是对现在或将来事情的推测判断，所以B，D选项不正确。根据句意排除C选项，故A 为正确选项。