Question

what reason can be used to justify the following statements: $angle1congangle2$ and $angle3congangle4$
vertical angles are congruent.
complements of congruent angles are congruent.
corresponding angles are congruent.
supplements of congruent angles are congruent.

Explanation:

Vertical angles are formed when two lines intersect. $\angle1$ and $\angle2$ are vertical - angles, and $\angle3$ and $\angle4$ are vertical - angles. By the vertical - angle theorem, vertical angles are congruent.

Answer:

Vertical angles are congruent.