— Come and join us, Ben!— I'm afraid I can't. I'm too busy now. If I ________ time, I would certainly go.
A：had
B：will have
C：have had
D：have
标志着国共两党第二次合作初步形成的历史事件是( )
Mum ____ (mop) the floor when I got home yesterday.
纸币上的民族你知道哪些？
