螺纹紧固的四种错误：（）；（）、紧固工具的错误、紧固连接件的错误。
参考答案：紧固作业者的错误、紧固方法的错误
John was dismissed last week because of his _____ attitude towards his job. [ ]
A. informal
B. casual
C. determined
D. earnest
在使用无腿碹胎时（）。
A.碹的墙体插入端要用石料挤牢
B.碹胎之间有拉杆
C.为搬迁方便，碹胎可做成两节的
