对CK有激活作用的离子是（）。
A．Mg2+
B．Cl-
C．Fe2+
D．Cu2+
E．
参考答案：A
Many people agree that there has never been a more splendid opening ceremony than _______ of the Guangzhou Asian Games in history.
A．one
B．that
C．which
D．this
水泵在1500~3000转/分时，泵的径向振幅不超过（）。
