题目

When I knew Mary made every effort ______ the homeless, I could not but ______ her.    A. to help; admire   B. to help; to admire     C. helping; admire               D. help; admiring 答案：A 解析: 略3．设f（x）是定义在R上的增函数，且对任意x，都有f（-x）+f（x）=0恒成立，如果实数x，y满足不等式f（x2-6x）+f（y2-4y+12）≤0，那么$\frac{y-2}{x}$的最大值是（　　）A．1B．2C．$2\sqrt{2}$D．$\frac{{\sqrt{2}}}{4}$