Answer:
B.
, Converse of the alternate interior angles theorem
Explanation:
We are given that

We have to find the lines must be parallel based on given information .
To find the parallel lines we will use converse of alternate interior angles theorem.
Converse of alternate interior angles theorem: When alternate interior angles are equal then the lines are parallel.

Reason: Given
Angle 3 and angle 13 are alternate interior angles
Therefore, by using converse of alternate interior angles theorem
Line a and b are parallel.
Hence, option B is true.