已知定义在\(R\)上的函数\(f(x)\)满足\(f(x+6)=f(x)\)，\(y=f(x+3)\)为偶函数，若\(f(x)\)在\((0,3)\)内单调递减\(.\)则下面结论正确的是\((\quad)\)
A. \(f(10)< f(e^{\frac{1}{2}})< f(\ln 2)\)
B. \(f(e^{\frac{1}{2}})< f(\ln 2)< f(10)\) C. \(f(\ln 2)< f(10)< f(e^{\frac{1}{2}})\) D. \(f(\ln 2)< f(e^{\frac{1}{2}})< f(10)\)
