单项选择题 应力变化反复的场合的管道采用法兰连接时，其连接法兰的形式为（）。

单项选择题 听力原文：M: Excuse me, I bought this watch last Saturday. It's supposed to be waterproof, but it doesn't work now. I'd like my money back.W: I completely understand, sir. But usually we don't give money back on reduced items. Maybe you can speak to the manager.Q: What do we learn from the conversation?(17)A．The man bought the watch last Sunday.B．The manager can give money back to the man.C．The woman will speak to the manager about the matter.D．The waterproof watch was bought in the period of promotion.

多项选择题 不能输送氢氟酸、热磷酸和强碱的非金属管包括（）。