高等动物和人体有生殖系统、泌尿系统、____、____、____、____、____和内分泌系统等八大系统。

已知f（x）是偶函数，且f（x）在0，+∞）上是增函数，如果f（ax+1）≤f（x﹣2）在$x\in \frac{1}{2},1$上恒成立，则实数a的取值范围是（　　）

                                                                                  天净沙·秋思                       天净沙·春

                                                                             （元）马致远                         （元）白朴

                                                                               枯藤老树昏鸦，                    春山暖日和风，

                                                                               小桥流水人家，                    阑干楼阁帘栊①，

                                                                               古道西风瘦马。                    杨柳秋千院中。

                                                                               夕阳西下，                           啼莺舞燕，

                                                                               断肠人在天涯。                    小桥流水飞红②。

【注】①帘栊：带帘子的窗户。②飞红：花瓣飞舞，指落花。