Answer:
Angle 2 is supplementary to angle 8 because the two angles create a supplementary angle (180 degrees angle)
Explanation for the other options:
Angle 2 is not congruent to angle 5 but it is congruent to angle 6 because the corresponding angles postulate.
Angle 2 is not complementary to angle 5 because it does not create a complementary angle. Complementary angle is a 90 degrees angle.
Angle 2 is not congruent to angle 8 but it is congruent to angle 6 because of the corresponding angles postulate.