基线一般采用直线形，其长度一般不小于桥轴长度的( )倍。
A．2～1．B．0.7～0.5．C．1.5～1．D．0.9～0.7
参考答案：B
—Mary can't help ______ the house. Why?
—Because she is busy______ a hotel reservation.
A. cleaning; making B. to clean; making C. cleaning; to make
从供给或消耗的观点可将调速工具分为哪几种？
