（）不是二氧化碳吸收系统发泡时的现象。
A、接触塔压差上升
B、再生塔液位上升
C、碳酸盐溶液闪蒸罐液位下降
D、接触塔分离罐液位上升
参考答案：B
设集合U={1，2，3，4，5}，A={1，2，3}，B={2，4}，则A∩（CUB）=[ ]
A.｛1，3｝
B.｛2，4｝
C.｛1，2，3，5｝
D.｛2，5｝
There _____ a lot of coal mines in the south, but many of them have been closed or are _____ be closed.
A．use to having; about to
B．used to be; to
C．use to having; going to
D．used to be; supposed to
