Which statement is CORRECT about a pair of vertically opposite angles?

When two straight lines intersect, four angles are formed. They satisfy two key properties:

**Linear Pair Axiom**: If a ray stands on a line, the sum of the two adjacent angles formed is **180°**.

**Vertically Opposite Angles Theorem**: When two lines cross, the angles directly opposite each other are equal.

**Quick proof of vertically opposite angles**:
Let two lines intersect, forming angles ∠1, ∠2, ∠3, ∠4 (in order around the point).
- ∠1 + ∠2 = 180° (linear pair)
- ∠2 + ∠3 = 180° (linear pair)
- So ∠1 = ∠3 (subtract ∠2 from both). ✓