当pH值为（）左右时，析氢反应开始，使铁迅速溶解。
A、4
B、5
C、5.5
D、6
参考答案：A
—What do you plan to do for the homeless people?
—I want to ______ some clothes ______ them. [ ]
A. provide; with
B. provide; for
C. give; with
D. buy; to
直流电动机宜采用调节电源电压或电阻器降压起动，起动电流不宜超过电动机额定电流的( )倍。
A．1.5 B．1.4 C．1.3 D．1.2
