In the given figure OA, OB are opposite rays and $\angle$ AOC + $\angle$ BOD = ${90}^0$, then $\angle$ COD is

The correct option is A ${90}^0$
A straight angle always measures ${180}^o$

Given that, $\angle AOC+\angle BOD={90}^o$

But, $\angle AOC+\angle BOD+\angle COD={180}^o$ (straight angle)

$\therefore \angle COD$ = $180$ - $\angle AOC+\angle BOD$

$\therefore \angle COD$ = $180-90={90}^o$