调节阀按其能源形成可分为气动调节阀、电动调节阀和()调节阀。
A.手动
B.机械
C.液压
D.磁力
参考答案:C
20÷6.6的商保留两位小数约是3.03.______.
Don’t do such things again,young man.________,you are not a child any longer.
A.First of all
B.After all
C.All over
D.Above all