加热炉产生回火的原因（）
A、瓦斯压力过高
B、炉膛负压过底
C、配风量过大，也会使火嘴瓦斯瞬间中断而产生回火
参考答案：C
Once the durations of the activities are calculated for a completed network, a forward pass and a backward pass will provide ______.
A) the float of the activitiesB) the early start and late start onlyC) the critical pathD) A and C
广州生产的珠江啤酒是全国三大啤酒品牌之一。
