当一天用水量大且均匀时，由于这种工况下用水与送水曲线相近，可选用( )。

A．恒速水泵

B．高位水箱

C．变频调速水泵

D．变速水泵

With time changing so fast, to keep _____ with time, anyone should be a lifelong learner, or he will fall behind within years.

A．pace

B．stage

C．fare

D．Attitude