题目

Many Chinese children have to take piano lessons, but few of them have  ____   in it.    A. duty           B. courage           C. experience       D. interest 答案：D 如果函数f(x)＝ax(ax－3a2－1)(a＞0且a≠1)在区间[0，＋∞)上是增函数，那么实数a的取值范围是 [　　] A． B． C． D．