-Where has all the time gone? I can still remember the day when I first came to this school, but now I am about to leave.

-_______.

A．That makes two of us

B．One is never too old to learn

C．I don't have a clue

D．The grass is always greener on the other side of the fence

使用有功功率标准的装置检定无功功率标准，如何减少三相电路不对称的影响？