题目

 The mother thanked the young man again and again, without ______ help her son would have been washed away in the flood. A. whom           B. his              C. whose                D. who 答案：C已知函数（）（1）若曲线在点处的切线平行于轴，求的值；（2）当时，若直线与曲线在上有公共点，求的取值范围.