When parallel lines are cut by a transversal, which of these statements must be true about the measures of vertical angles? A
They are equal to each other, because one vertical angle is supplementary to the other.

B
They are equal to each other, because one vertical angle is a reflection of the other.

C
They are not equal to each other, because one vertical angle is not supplementary to the other.

D
They are not equal to each other, because one vertical angle is not a reflection of the other.