Consider the following C functionvoid swap $($int a$,$ int b$)\{$int temp;temp $=$ a;a $=$ b;b $=$ temp;In order to exchange the values of two variables x and y$.$O a$.$ Call swap $($x$,$ y$)$Ob$.$ Call swap $($&x$,$ &y$)$Oc$.$ swap$($x$,$y$)$ cannot be used as it does not return any valueOd. swap$($x$,$y$)$ cannot be used as the parameters are passed by value