铅衬里的固定方法有搪钉固定法、( )、压板固定法(焊接式)等。A．封闭衬里 B．上

动词填空， 用所给动词的适当形式完成下列短文。

     John 1_____ (study) at the town's school now, He 2_____  (be) there since last year. He isn't interested

in studying. He 3_____  (prefer) to make friends and spend a lot of time outside. He also likes 4_____  (play)

computer games with his friends. So of course, when the exam 5_____  (take) last week, he didn't get a good

result and 6_____  (fail) again. He thought, "If my father knows all about it, he 7_____  (become) angry and

give me a good lesson," So he sent a note to his brother and asked his brother to get his father ready for the

bad news. The next morning, he received the following answer, "Father is ready. You'd better 8_____ (be)

ready for yourself."

从产业发展的生命周期理论的角度来看，支柱产业是处于（）的产业.

A.成长期

B.衰退期

C.成熟期

D.形成期

水飞法

选题时要看是否有足够的合格研究者及辅助人员，指的是选题过程要遵守（）

A.主观性标准

B.重要性标准

C.新颖性标准

D.可行性标准

汽包电接点水位计电极更换时，应做好哪些安全上和技术上的工作？