A：has not heard of
B：had not heard of
C：has not been heard of
D：had not been heard of
当a= ____时，|1﹣a|+2会有最小值，且最小值是 ____
—No, I can't. Well, I can cook eggs. But .
西双版纳的气候类型是____。
函数y=log12x2-2x的单调递减区间是____
