、熔化焊过程中的有害因素可分为焊接烟尘、（）、电磁辐射、光热伤害、振动和噪声等几类。
参考答案：有毒气体
I don't think he could have done such a stupid thing last night, ______? [ ]
A. do I
B. could I
C. did he
D. has he
( )承重建筑物的全部荷载，是建筑物的一部分。
A．地基B．基础C．柱D．承重墙
