1. The left and right directrices $l_{1} 、 l_{2}$ of the hyperbola $\frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=1$ trisect the line segment $F_{1} F_{2}$ ($F_{1} 、 F_{2}$ are the left and right foci of the hyperbola, respectively). Then the eccentricity $e$ of the hyperbola is ( ).
(A) $\frac{\sqrt{6}}{2}$
(B) $\sqrt{3}$
(C) $\frac{3 \sqrt{3}}{2}$
(D) $2 \sqrt{3}$
1. B.
From $2 c=3 \times \frac{2 a^{2}}{c} \Rightarrow e=\sqrt{3}$.