Confused

i think a

Given that AB = AC, BD = BD(bc it's just the same), and angle ABD = angle CBD

First B can be used.

C can be used because hypotenuse and one side is equal

D can be used because angle ADB = angle CDB = 90 deg

A still can be used because we can use the right angles and 2 pairs of equal sides to derive that the remaining pair of sides are equal......

This is a bad question......