题目

Why do some rich people steal things ____ they could easily afford to buy them?        A．unless        B．before                 C．if                    D． when 答案：D11、已知函数f（x）=xex（e为自然对数的底）．（1）求函数f（x）的单调递增区间；（2）求曲线y=f（x）在点（1，f（1））处的切线方程．