Ah, looks like a special right triangle to me, just got done learning about these.
Alright, so, since this is a 30-60-90 triangle, 6 is the smallest leg (as across from 30 degree is the smallest leg), labeled as s. Across from the 90 is 12, as that is 2s.
The missing side, across from the sixty, would be 6 square root of 3 (fourth answer).