若导体两端的电压提高一倍，则电功率是原来的（）倍。
A、4
B、2
C、8
D、1
参考答案：A
The Mekong River Commission has found no evidence the dams on the upper reaches have an influence on the water flow downstream.
A．that
B．which
C．where
D．what
It has calculated that the earth's circumference around the equator is over forty miles longer than that around the poles.
