题目

．— Has Tom finished his report so far?        — I have no idea．He ______it this morning．        A．did                    B．has done        C．was doing           D．had done 答案：C已知函数.（Ⅰ）当时，求曲线在点处的切线方程；（Ⅱ）求的单调区间；（Ⅲ）若在区间上恒成立，求实数的取值范围.