A ) ∠2 is supplementary to angle ∠3
Justification: Collateral internal angles are always supplementary to each other.
B) b║a
Corresponding angles are congruent between themselves.
c) ∠1 and ∠12 are supplementary angles
∠1 and ∠2 are congruent, and ∠2 is supplementary to angle ∠12 that is why ∠1 and ∠12 are supplementary
d) ∠9≅∠12
Vertical angles are always congruent