原式=6+13+23+(-4.6-0.4-2.3)
=6+1-7.3
=-0.3.
Changes often happen in ______.
A.Initiating Process
B.Executing Process
C.Planning Process
D.Closing Process
下列各机械()属于工作机
A.泵
B.透平
C.内燃机
D.通风机