—Did you have fun _____________ on your last day off?
—No, I didn't. there were too many people and it was really crowded.
A:shop
B:shopping
C:to shop
D:shopped
下列属于长江沿江经济发达地带的中心城市是
— No, there aren't.
NA为阿伏伽德罗常数的值.下列说法正确的是( )
下列哪次战役是第一次世界大战的转折点( )
由于x2≥0,所以x2有最小值0,从而x2+1有最小值1.据此请求出(1)x2﹣2的最小值;(2)x2﹣4x+1的最小值;(3)﹣x2+3x+2有最大值还是最小值呢?请你求出这个最大或最小值来.