For every ten yards on a football field there is a boldly marked line labeled with the amount of yards. Each of those lines is perpendicular to both sidelines. What can be said about the relationship of the sidelines? Justify your answer.

A. The sidelines are perpendicular to each other by the definition of the Transitive Property
B. The sidelines are parallel by the Same-Side Interior Angles Theorem
C. The sidelines are perpendicular by the Perpendicular Transversal Theorem
D. The sidelines are parallel because they are perpendicular to the same line.