____ the chat room ten minutes ago, you would have known what we were talking about! [ ]
A. Had you joined in
B. If you joined
C. If you had joined in
D. Had you joined
答案:D
____ the chat room ten minutes ago, you would have known what we were talking about! [ ]
A. Had you joined in
B. If you joined
C. If you had joined in
D. Had you joined
答案:D