题目

函数f(x)＝x3＋ax2－3x－9,已知f(x)的两个极值点为x1,x2,则x1·x2＝( ) A.9         B.－9          C.1           D.－1 答案：DTomorrow he_______ a kite, and then_______ boating.A. will fly; will go B. will fly; goesC. is going to fly; will goes D. flies; will go A 【解析】句意：明天他要去放风筝，然后去划船。根据Tomorrow可知用将来时态，结构是：will do 或者be going to do；故选A