6. The equation of the ellipse is $\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1(a>b>0)$, with the left vertex being $A$, the left and right foci being $F_{1}, F_{2}$, and $D$ being one of the vertices on its minor axis. If $3 \overrightarrow{D F_{1}}=\overrightarrow{D A}+2 \overrightarrow{D F_{2}}$, then the eccentricity of the ellipse is
A. $\frac{1}{2}$
B. $\frac{1}{3}$
C. $\frac{1}{4}$
D. $\frac{1}{5}$
Solve:
$\overrightarrow{D F_{1}}=\frac{1}{3} \overrightarrow{D A}+\frac{2}{3} \overrightarrow{D F_{2}} \Rightarrow \overrightarrow{A F_{1}}=\frac{2}{3} \overrightarrow{A F_{2}} \Rightarrow a-c=\frac{2}{3}(a+c) \Rightarrow a=5 c \Rightarrow e=\frac{1}{5}$, so the answer is $D$.