A．在水中快
B．在空气中快
C．在铜中快
D．在三种物质中一样快
答案：C
地球运动形成了五带，临沂市（位于北回归线与北极圈之间）属于（ ）
You should _____ your mother _____ help when you can't do the washing.[ ]
A. ask; with
B. ask; for
C. ask; in
D. ask; on
