曲轴有（）部分组成。
A.2
B.3
C.4
D.5
参考答案：D
One of the best ways for people to keep fit is to _______ healthy eating habits.
A．grow
B．develop
C．increase
D．raise
1000BASE-LX标准支持的传输介质是( )。
A．单模光纤
B．多模光纤
C．屏蔽双绞线
D．非屏蔽双绞线
