手工钨极氩弧焊机的组成包括焊接电源、高频振荡器、焊枪、供气系统、控制系统和（）。
参考答案：冷却系统
卡他性炎常发生在（）。
A.肌肉
B.皮肤
C.黏膜
D.浆膜
E.实质器官
The acid rain is one of the chain reactions that ______ by environmental pollution . [ ]
A. is come about
B. is caused
C. are given birth
D. are brought about
