The diagram shows parallel lines cut by two transversal lines creating a triangle. Which statements are true? Check all that apply. m∠A = 20° ∠B and the angle marked 60° are alternate exterior angles. m∠C = 100° because it is a vertical angle to the angle marked 100°. ∠B and ∠C are supplementary angles. m∠A + m∠B + m∠C = 180°