In each of the​ following, fill in the word needed to make the resulting sentence true.
a. A quadrilateral is a​ ____ if, and only​ if, its diagonals bisect each other. nothing nothing
b. A quadrilateral is a​ ____ if, and only​ if, its diagonals are congruent and bisect each other. nothing
Fill in the word needed to make the resulting sentence true. If none of the words makes the sentence​ true, choose​ 'none.'
a. A quadrilateral is a parallelogram
​if, and only​ if, its diagonals bisect each other. nothing nothing
b. A quadrilateral is a rectangle
​if, and only​ if, its diagonals are congruent and bisect each other. nothing