题目

Hengshui will soon take on a new look as many roads and streets widened or rebuilt. A . had been B . have being C . are being D . were being 答案：C（湖南卷理14）已知函数 （1）若a＞0,则的定义域是           ; (2) 若在区间上是减函数，则实数a的取值范围是             .