The figure below shows parallel lines cut by a transversal: A pair of parallel lines is shown, cut by a transversal. Angle 7 is located in the upper right exterior corner on the top line, and angle 8 is located in the upper left exterior corner of the top line.

Which statement is true about ∠7 and ∠8?

∠7 and ∠8 are supplementary because they are a pair of corresponding angles.
∠7 and ∠8 are complementary because they are a pair of adjacent angles on a straight line.
∠7 and ∠8 are congruent because they are a pair of adjacent angles on a straight line.
∠7 and ∠8 are supplementary because they are a pair of adjacent angles that form a straight line.