Select the correct answer from each drop-down menu. ∆ABC has the points A(1, 7), B(-2, 2), and C(4, 2) as its vertices. The measure of the longest side of ∆ABC is units. ∆ABC is triangle. If ∆ABD is formed with the point D(1, 2) as its third vertex, then ∆ABD is triangle. The length of side AD is units.