天然气在空气中可燃性限界范围很窄，因此，在燃烧过程中对缺氧很敏感，同时减少了回火的危险性。
参考答案：对
-I don't feel like going out. Why don't we stay at home and watch TV?
- _________ You promised to take me out for a ride. [ ]
A. Really?
B. Not at all.
C. Come on !
D. No matter.
第二象限内的点P（x，y）满足|x|=5，y2=4，则点P的坐标是______．
