Alex is writing statements to prove that the sum of the measures of interior angles of triangle pqr is equal to 180°. line m is parallel to line n. line n is parallel to line m. triangle pqr has vertex p on line n and vertices q and r on line m. angle qpr is 80 degrees. segment pq makes 40 degrees angle with line n and segment pr makes 60 degrees angle with line n. which is a true statement he could write? angle prq measures 40°. angle pqr measures 60°. angle prq measures 80°. angle pqr measures 40°.