What is the scope of $$x

in the formula $$x$($p$($x$)$yq$($x$,$y$))$

$?$

a$.$

$$x$($p$($x$)$yq$($x$,$y$))$

b$.$

p$($x$)$yq$($x$,$y$)$

c$.$

p$($x$)$q$($x$,$y$)$

d$.$

p$($x$)$