发电厂主蒸汽管道系统主要有()等形式。
参考答案:单元制系统、切换母管制系统、集中母管制系统、扩大单元制系统
11. Don't judge a person only by his _____.
A.look
B.appearance
C.appearances
D.Faces
起重机调速性能都较差,多采用()进行。