Tom's parents are busy ______ some cakes and ______ ready for the party.[ ]

A. buy; make

B. buying; getting

C. to get; have

D. buying; to be

引起皮带跑偏的因素有（）。

A.下料点不正

B.皮带档破

C.皮带接头不正

D.纠偏器不起作用