单项选择题
Foaming in the steam drum may be caused by （） in a boiler.
A.oxygen in the water B.poor boiler design C.density too high D.excessive steam demand
单项选择题 Too much air in the furnace of an oil-fired boiler would be indicated by （）.
单项选择题 The feed water to the boiler will comprise （）.
单项选择题 Proper combustion in a boiler would be indicated by （）.
