Of the two brothers, Bill is ______ younger one, and he is a quiet boy, ______ that most adults like very much.

A．the; one

B．a; the one

C．a; one

D．the; the one

工业用泵和农用泵的分类依据是( )。

A．输送液体性质不同

B．托架的支撑方式不同

C．泵的性能不同

D．使用部门不同