为了保证离心泵不发生汽蚀,泵的必须汽蚀裕量应大于装置的汽蚀裕量。
参考答案:错
June the first is ____________ Day.[ ]
A. Children
B. Childrens
C. Childrens'
D. Children's
灰口铸铁的可锻性极好。