A:hardly; good
B:hard; well
C:hardly; best
D:hard; the best
函数f(x)=axx<0a-3x+4ax≥0满足f(x1)﹣f(x2)(x1﹣x2)<0对定义域中的任意两个不相等的x1,x2都成立,则a的取值范围是____
中国古代经济曾经有许多方面取得辉煌成就。下列图片所示成就,按年代顺序排列正确的是( )
Our teacher walks to school every day.