设置机械排烟的地下室，应同时设置送风系统，并且送风量不宜小于排烟量的______。
A．50% B．40% C．30% D．20%
参考答案：A
---We think it is wrong ______ him ______her copy the homework.
A．of; to help
B．for; to help
C．of; helping
D．for; helping
