三相四线制A.B.C.N的颜色顺序为()
A.黄.绿.红.蓝
B.绿.黄.红.蓝
C.黄.绿.红.黄绿
D.蓝.红.黑.黄
参考答案:A
-I'm sorry I __________ my exercise book at home.
-Don't forget __________ it to school tomorrow, please.[ ]
A. forgot, to take
B. left, to bring
C. forgot, to bring
D. left, to take
焊接应力与变形产生的原因是什么?减小和消除焊接应力的措施有哪些?