题目

If you want to make a fruit salad, you should choose fruit ________ and never leave it in the air for ______. Or it’ll turn brown quickly.    A. in a season, sometime       B. in season, some time C. in the season, sometimes     D. in season, some times 答案：B6．在等差数列{an}中，a1+a3+a5=-3，a1•a3•a5=15，求它的通项公式．