Question

The adjacent supplementary angle to any of the interior angles of a triangle is called an exterior angle of a triangle.

Answer 1

Correct

Explanation:

The supplementary angle to any of the interior angles of a triangle is called an exterior angle, they are supplementary because they form a 180º angle when you extend a straight line from the adjacent side of the angle and any straight angle is a 180º angle, so supplementary angles added up would make 180º.