Line p intersects lines a and b. a b. By which theorem is ∠1 ≅ ∠8? A horizontal line p cuts two parallel lines a and b transversely. The resultant angles formed by the intersection of the lines a and p are labelled 1, 2, 3 and 4 and those formed by the intersection of the lines b and p are labelled 5, 6, 7 and 8. A. Alternate Exterior Angles Theorem B. Alternate Interior Angles Theorem C. Corresponding Exterior Angles Theorem D. Corresponding Interior Angles Theorem