多项水质参数综合评价在（）应用。
A.调查的水质参数大于3项时
B.调查的水质参数大于等于1项时
C.调查的水质参数较多时
D.任何情况都可用
参考答案：C
已知集合A={2，4}，B={2，3，4}，C={(x，y)|x∈A，y∈B，且logxy∈N*}，则C中元素个数是（ ）
A．2
B．3
C．4
D．5
— made Daisy wild with joy？
—Her success in the A-level exam this year.
A．How was it that
B．When was it that
C．Why was it that
D．What was it that
