题干
Don't talk loudly at the meeting. If you ________, you will have to leave.
A：do
B：are
C：did
D：have done
答案(点此获取答案解析）
A
Don't talk loudly at the meeting. If you ________, you will have to leave.
A：do
B：are
C：did
D：have done
，则用含n的代数式表示 
为