16. The side between the marked angles is congruent to itself. The angle marks indicate the angles on either end of that side are congruent. So, you have ... congruent Angle, congruent Side, congruent Angle. The appropriate choice is
... ASA
17. All of the given choices have pairs of parallel sides. However, only the rhombus and the square have perpendicular diagonals. The diagonals in a square are necessarily the same length, but that is not a given fact. So, we can only say for sure the figure is a
... rhombus
