— Are you still busy?

— Yes, I ____ my homework, and it won't take long. [ ]

A. just finish

B. am just finishing

C. have just finished

D. am just going to finish

室内给水系统水泵串联的目的是（）

A、增加扬程，流量不变

B、减少流量

C、增加流量

D、减少扬程