问题补充:
If you had joined the chat room ten minutes ago, you what we were talking about!
A. have known
B. knew
C. would have known
D. would know
答案:
A. have known
B. knew
(答案→)C. would have known
D. would know
解析:考察虚拟语气的用法。根据If you had joined the chat room可知,该句是表示对过去的虚拟,主句选用would have done结构
句意为,如果你早十分钟进入聊天室的话,你就会知道我吗在讨论什么了。