Answer:
(b) _Congruent
Explanation:
You want to know the relationship between corresponding angles where a transversal crosses parallel lines.
Corresponding angles
The Corresponding Angles theorem tells you that corresponding angles at a transversal are congruent if and only if the lines are parallel.
Corresponding angles are congruent.
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Additional comment
This fact is the basis for the simplest method of constructing a line parallel to a given line through an external point. (A transversal is drawn, and the angle is copied, making congruent corresponding angles.)
All of the other angle relationships at a transversal can be derived from this one using the usual relationships of linear pairs and vertical angles.