Examine the diagram.

2 parallel lines are cut by 2 transversals. Angles A, 100 degrees, and B form a straight line. Angle C is a vertical angle to the angle marked 100 degrees. Angle B is 60 degrees.

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°