题干
听录音，补全短文中所缺的单词
Fire is very dangerous. It can ____people. We ____be careful with fire. We mustn't play near fires. We mustn't play with matches. We mustn't ____in the forest. When we see a fire, we must go outside ____，but ____use the lift.
答案(点此获取答案解析）
hurt,must,smoke,quickly,never
后面第30个是三角形。
，现给出下列命题：
=
;
时，不等式
恒成立；
是偶函数 . 其中正确的命题是 （ ）