Answer: The correct option is
(B) Corresponding angles are congruent.
Step-by-step explanation: Given that a student was told to consider the diagram and asked to prove that angle 1 ≅ angle 2.
We are to find the reason for the second step in the following proof :
(1) Line A and B are parallel Given
(2) ∠1 ≅ ∠3 ?
(3) ∠2 ≅ ∠3 ?
(4) ∠1 ≅ ∠2 ?
Since lines A and B are parallel and cut by a transversal, so angles 1 and 3 are corresponding angles. That is, ∠1. ≅ ∠3
Also, angles 2 and 3 are vertically opposite angles, so ∠2 ≅ ∠3.
And, therefore we get
∠1 ≅ ∠2.
Thus, the reason in the second step will be
angles 1 and 3 are corresponding angles and corresponding angles are congruent.
Option (B) is CORRECT.