#### Answer

Since $AD = CD$ and $AB = BC$, the quadrilateral $ABCD$ is a kite.

#### Work Step by Step

We know that $\angle DAB = \angle DCB = 90^{\circ}$
$AD = CD$, because each line is a radius of the circle.
We can use the Pythagorean theorem to show that the length of $AB$ is equal to the length of $BC$:
$AB = \sqrt{(BD)^2-(AD)^2}$
$AB = \sqrt{(BD)^2-(CD)^2}$
$AB = BC$
Since $AD = CD$ and $AB = BC$, the quadrilateral $ABCD$ is a kite.