对非火灾区域及疏散通道应迅速采用机械加压（）火灾区域的空气压力。
A、高于
B、低于
C、等于
D、不大于
参考答案：A
学校体育组买来8个足球，每个a元，又买来b个篮球，每个25.5元，那么8a+25.5b表示______．
By the time these books were published, he _____ addicted to them.
A．had become
B．becomes
C．has become
D．became
