与低比转数的水泵相比，高比转数的水泵具有（）

A.流量小、扬程高

B.流量小、扬程低

C.流量大、扬程低

D.流量大、扬程高

For seven days after the mud-slide, they had only grass and tree leaves to subsist upon.

A．made food out of

B．substitute for beds

C．live upon by eating

D．insist on keeping to themselves