下列行为不会造成空气污染的是[ ]
A、秋收后燃烧秸秆肥田
B、大量购买汽车
C、用煤炉生火烧饭
D、推广使用天然气
答案：D
设函数f(x)＝xex，则( )．
A．x＝1为f(x)的极大值点
B．x＝1为f(x)的极小值点
C．x＝－1为f(x)的极大值点
D．x＝－1为f(x)的极小值点
After that, he knew he could __ any emergency by doing what he could to the best of his ability.
A．get away with
B．get on with
C．get through
D．get across
