题目

-----Would you mind if I _____ here? -----Certainly not. Please go ahead. A. will smokeB. did smoke    C. smokedD. am smoking   答案：Cwould you mind if…….中的从句一般要用虚拟语气。已知f（x）=x3+x2f′（1）+3xf′（-1），则f′（1）+f′（-1）的值为     ﹒