题目

Obama says he is angry about policies that always favor the wealthy and powerful over     __________ Americans and Insists that opportunities be opened up to all．     A.average           B.intelligent    C.competitive     D.original 答案：A10．已知函数f（x）=$\left\{\begin{array}{l}xlnx-a{x^2}，x≥1\\{a^x}，x＜1\end{array}$是减函数，则a的取值范围是（　　）A．$（0，\frac{1}{2}]$B．（0，1）C．$（\frac{1}{2}，1）$D．$[\frac{1}{2}，1）$