六缸发动机闭合角的标准值（分电器凸轮轴转角）应为（）。
A.35～38°
B.38～42°
C.42～45°
参考答案：B
Nowadays people have many ways to communicate ________ their friends.[ ]
A) at
B) with
C) to
D) of
Z151蒸汽吊车空重为89.1吨。
