题目

The traffic rule says young children under the age of four and ________ less than 40 pounds must be in a child safety seat.  A. being weighed       B. to weigh                 C. weighed               D. weighing 答案：D已知函数f（x）=lg（x2-ax+3a），若对于任意的x∈[2，+∞），当△x＞0时，恒有，则实数a的取值范围是________．