瓦斯爆炸要同时具有以下哪几具条件:()
A.瓦斯浓度5-16%
B.引爆火源650-750
C.氧气浓度≥12%
参考答案:A, B, C
连铸坯的低倍组织是由表面细小等轴晶、()、中心等轴晶三个带组成。
The quality of the above mentioned goods were in conformity ( ) the requirement of the contract No. JBD-089.
A.with
B.in
C.under
D.of