Until he spoke, I hadn’t realized he didn’t know a...

Câu hỏi: Until he spoke, I hadn’t realized he didn’t know anything about the subject.    

A If he didn’t speak, I wouldn’t realize he didn’t know anything about the subject.

B If he hadn’t spoken, I wouldn’t have realized he didn’t know anything about the subject.

C Unless he spoke, I wouldn’t realize he didn’t know anything about the subject.

D When he spoke, I hadn’t realized he didn’t know anything about the subject.