If one of the angles formed by two intersecting lines is a right angle,what can you say about the other three angles? Give reason for your answer.

(D) Let two lines $AB$ and $CD$ intersect at point $O$. Let $\angle AOC = 90^\circ$.
Since $AB$ is a straight line,$\angle AOC + \angle BOC = 180^\circ$ (Linear pair axiom).
$90^\circ + \angle BOC = 180^\circ \implies \angle BOC = 90^\circ$.
Similarly,$\angle AOC + \angle AOD = 180^\circ$ (Linear pair axiom).
$90^\circ + \angle AOD = 180^\circ \implies \angle AOD = 90^\circ$.
Finally,$\angle AOD + \angle BOD = 180^\circ$ (Linear pair axiom).
$90^\circ + \angle BOD = 180^\circ \implies \angle BOD = 90^\circ$.
Therefore,all other three angles are also right angles $(90^\circ)$.