.--Your parents were anxious about you. You home without saying a word.
-- It’s my fault.
A. mustn’t be
B. shouldn’t have left
C. needn’t have left
D. couldn’t have left
网友回答
A. mustn’t be
(答案→)B. shouldn’t have left
C. needn’t have left
D. couldn’t have left
解析：考查虚拟语气.句意,你的父母很担心你.你不应该没说一句话就离家了.——那是我的失误。可知问句中表示的是对过去的推测。故选B最符合语境。