2. In the dihedral angle $P-a-Q$ of $120^{\circ}$, there are points $A$ and $B$ on the planes $P$ and $Q$ respectively. It is known that the distances from points $A$ and $B$ to the edge $a$ are 2 and 4, respectively, and the line segment $AB = 10$, and the angle between $AB$ and plane $Q$ is $\alpha$, then ( ).
(A) $\alpha=\arcsin \left(\frac{1}{5} \sqrt{\frac{21}{22}}\right)$
(B) $\alpha=\frac{\pi}{6}$
(C) $\alpha=\arcsin \frac{\sqrt{3}}{10}$
(D) None of the above
2. Draw $B D^{\prime} / / C D$ through $B$, and draw $C B^{\prime} / / B D$ through $C$ intersecting $B B^{\prime}$ at $B^{\prime}$. Then the plane $A B^{\prime} C$. 1's face $Q$.
Draw..

$A F$ perpendicular
line $B^{\prime} C$ at
$E$, then $A E \perp$
plane $Q$. So, $\angle A B E \angle$
is the angle $\alpha$ formed by $A B$ and
plane $Q$.
It is easy to find $A E=\sqrt{3}$. Therefore, $\sin \alpha=\frac{\sqrt{3}}{10}$.
$a=\arcsin \frac{\sqrt{3}}{10}$.
Choose C.