题目

补全对话，阅读下面对话，从方框中选择适当的句子补全对话（其中有两项是多余的）。A: Hello!B:   1     A: Well, would you please give me some advice on how to remember English words?B:   2      In fact, I learn English words by heart.A:   3    B: First of all, it is necessary for you to have a good habit of remembering them. A:   4    B: No, you don’t need to. Try to learn by heart a few new words each day, follow the rules of pronunciation and you will finish remembering all of them in one week.B:   5   I’ll try my best. Bye!A: 若函数f(x)=x2+3x-4x-1(x＞1)n+x3(x≤1)在x=1处连续，则(x+1x-2)n展开式中常数项是（　　） A、70B、-70C、140D、-140