采用洁净的（）清洁电磁制动器动静衔铁表面杂物。
A、棉布
B、毛刷
C、钢丝刷
D、铲刀
参考答案：A
（）是确定水泵安装高度的主要参数。
People had been conscious of the problem before, but the new book made them aware of its______.
A．multitude
B．magnitude
C．altitude
D．latitude
