The answer is C.
You want:
10 < a < 14 (greater or equal)
The difference between 10 and 12 is 2.
The difference between 12 and 14 is 2.
Therefore the absolute value allows you to express that the difference between a and 12 cannot be greater than 2 (either going up to a max of 14 or going down to a minimum of 10).
