树脂层中悬浮物增多是固定床逆流再生钠离子交换器（）的原因之一。
A、工作交换能力下降
B、出水硬度超标
C、中排装置损坏
D、排水装置损坏
参考答案：A
They asked the students ______ as soon as possible. [ ]
A. answered
B. to reply
C. answering
D. replying
The specialist, ______ some of his assistants, ____ to attend our discussion.
A．and; is
B．or; are
C．as well as; is
D．except for; are
