题目

Someone in the crowd called out his name, but he couldn’t see ______. A. whose                  B. who                      C. where             D. which 答案：B15．已知函数f（x）=|x-10|-|x-25|，且关于x的不等式f（x）＜10a+10（a∈R）的解集为R．（1）求实数a的取值范围；（2）求2a+$\frac{27}{{a}^{2}}$的最小值．