乙炔用以下气体稀释后爆炸能力会降低,如N2(1:1)时、CH4(甲烷)、CO2、CO、H2O(水蒸气)等,效果最好是()
A、N2
B、CO2
C、H2O
参考答案:A
—What is your English teacher like?
—________. [ ]
A. She likes fruit and vegetables.
B. She is fine
C. She is very kind
工件经热处理后,其强度、硬度较退火为高,而且生产周期短,能耗低,故在可能的情况下应优先考虑,此种热处理工艺为()。
A.正火工艺
B.淬火工艺
C.回火工艺
D.高温回火工艺