管道强度试验合格后,降压至设计压力,检验有无泄漏,使用的检查方法为()。
A.刷煤油
B.刷肥皂水
C.刷碱液
D.涂白垩水
参考答案:B
.Part of the family _______ out on holiday. They are supposed to be back at the end of this week.
A.is
B.are
C.was
D.were
个人通信就是一种进行()各种业务通信的通信方式。