Question

Triangle ABC is shown below.

Answer 1

The correct answer (though it is not one of the choices) is:

Alternate Interior Angles Theorem.

Explanation:

Alternate interior angles are angles that are inside the parallel lines and on opposite sides of the transversal.  Treating BA as a transversal, ∠DBA and ∠BAC are both inside the parallel lines and on opposite sides of BA, the transversal.  This makes them alternate interior angles, and means that they are congruent.