18连续减3:18、( )、( )、( )、( )。
15;12;9;6
---My new job is not as wonderful as I expected.
---Well, as the proverbs goes, “_________”
A.A year’s plan starts with spring.
B.A good beginning is half done
C.A light heart lives long.
D.The grass is always greener on the other side.
在下图所示的齿轮—凸轮轴系中,键2称为()
A.零件
B.机构
C.构件
D.部件