Answer:
A
. Alternate interior angles of parallel lines are congruent
Step-by-step explanation:
If you observe the image, the statement that Janet wants to justify is
[tex]\angle 1 \cong \angle A[/tex]
[tex]\angle 3 \cong \angle C[/tex]
According to the given graph, these angles are inside parallels because [tex]DE \parallel AC[/tex] by given, and these angles are at different sides of the transversals [tex]BA[/tex] and [tex]BC[/tex], those position define Alternate Interior Angles, which by theorem they are congruent.
Therefore, the right reason of such congruence is
A
. Alternate interior angles of parallel lines are congruent.