Answer: The correct option is (C) 6.
Step-by-step explanation: We are given a triangle ABC in the figure, in which

We are given to find the length of side AB.
In ΔABC, we have

We know that in a triangle,
if two angles have equal measures, then the sides opposite to them are equal in length.
So, we must have

Therefore, the length of AB will be

Thus, the length of side AB is 6 units.
Option (C) is CORRECT.