Question

A horizontal line has points D, B, C. A line extends vertically from point B to point A.
Given that Ray B A bisects ∠DBC, which statement must be true?

m∠ABD = m∠ABC
AB ≅ BC
B is the midpoint of DC.
m∠DBC = 90°

Answer 1

m∠ABD = m∠ABC

Reason: Ray BA bisects ∠DBC, so by definition it divides ∠DBC into two equal angles with vertex B: ∠ABD = ∠ABC. The other choices (congruence of segments, midpoint, or ∠DBC = 90°) do not follow.