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Select the correct answer from each drop-down menu. A triangle ABC with base AC is shown. A line DE, parallel to line AC, passes through vertex B. Interior angle at vertex A is labeled 1, at vertex C is labeled 3, and at vertex B is labeled 2. The exterior opposite angles at vertex B are 4 and 5. Points A, B, and C form a triangle. Complete the statements to prove that the sum of the interior angles of ΔABC is 180°. Statement Reason Points A, B, and C form a triangle. given Let be a line passing through B and parallel to . definition of parallel lines ∠3 ≅ ∠5 and ∠1 ≅ ∠4 m∠1 = m∠4 and m∠3 = m∠5 m∠4 + m∠2 + m∠5 = 180° angle addition and definition of a straight line m∠1 + m∠2 + m∠3 = 180° substitution