(05.06A)Angle ABC is formed by segments AB and BC on the coordinate grid below:
Which statement shows the measure of angle A′B′C′?
A. m∠A′B′C′ = 90 degrees
B. m∠A′B′C′ = 180 degrees
C. m∠A′B′C′ = m∠ABC
D. m∠A′B′C′ = 2 × m∠ABC
