标志n表示（）型防爆电气设备。
A.充砂
B.特殊
C.无火花
参考答案：C
Most air pollution is caused by the burning of ____ like coal, gas and oil. [ ]
A. fuels
B. articles
C. goods
D. products
简述无锡锅炉厂UG-1217/18.4-M型锅炉燃烧器的特点。
