题目

已知函数的最小正周期为,若在上单调递增,在上单调递减,则实数的取值范围是( )A. B. C. D. 答案：【答案】B【解析】由函数的最小正周期为可得，求出的增区间与减区间，分别令与是其子集即可.由题意可得，求得，令，求得，由，求得，因为在上单调递增,在上单调递减,所以，所以实数的取值范围是，故选B.He was a much older tennis player, but he had a (n)        over other players in experience.     A．profit   B．power    C．advantage    D．benefit