交流电压的波峰因数K_p定义为（）。

A.峰值与平均值之比

B.有效值与平均值之比

C.峰值与有效值之比

D.平均值与峰值之比

As we have known from the map of the woad, this is ______.

A．twice as large an island as that
B．twice as larger as that island
C．as twice as that one
D．twice as a large island as that