瓦斯爆炸的条件是具备（）。
A、一定浓度
B、一定引火温度
C、一定空气压力
D：充足氧气含量
参考答案：A, B, D
The artist spent years on his monumental painting, which covered the whole roof of the church, the biggest in the country.
A．archaic
B．sentimental
C．outstanding
D．entire
何谓折角车流？双三级六场编组站减少折角车流的方法有哪些？
