In the accompanying diagram, line t is parallel to line m, and lines s and t are transversals that intersect at a point in line m.
Which statement must be true?

A. Measure of angle 1=measure of angle 4

B. Measure of angle 1=measure of angle 2 + measure of angle 3

C. Measure of angle 5=measure of angle 2 + measure of angle 3

Explain your answer.