—What do you think we can do for our aged parents?

—You___do anything except to be with them and be yourself.

A．don’t have to

B．oughtn’t to

C．mustn’t

D．can’t

在同一块地里成行或成带（若干行）间隔地种植两种或两种以上生长期相近的作物，叫做（）。

A.间作

B.混作

C.套作

D.轮作