题目

 You can't imagine what difficulty he had ______ a customer to buy the high-tech product. A. persuaded               B. persuade              C. to persuade            D. persuading    答案：D已知函数f(x)=2x-1，(x∈[2，6])，则函数的最大值为（　　）A．0.4B．1C．2D．2.5