具有特解 $y_1= e ^{-x}, y_2=2 x e ^{-x}, y_3=3 e ^x$ 的 3 阶常系数齐次线性微分方程是
A. $y^{\prime \prime \prime \prime}-y^{\prime \prime}-y^{\prime}+y=0$
B. $y^{\prime \prime \prime}+y^{\prime \prime}-y^{\prime}-y=0$.
C. $y^{\prime \prime \prime}-6 y^{\prime \prime}+11 y^{\prime}-6 y=0$.
D. $y^{\prime \prime \prime}-2 y^{\prime \prime}-y^{\prime}+2 y=0$.