
This is a gre question so the Figure is not drawn to scale. So we can not guess that $BAD$ is right triangle. Can I evaluate these answer without knowing the right angle from the question?

This is a gre question so the Figure is not drawn to scale. So we can not guess that $BAD$ is right triangle. Can I evaluate these answer without knowing the right angle from the question?
The question directly states that ABCD is a rectangle, so you can safely assume that angles BAD, ADC, CDB and CBA are all right angles. It is impossible to find any of the answers otherwise.