This question is about the pumping lemma for context$-$free languages.

$($c$)$ Let $C=\{\begin{array}{ccc}\text{w}\text{i}\text{n}& \{a,b,c,& d{\}}^{*}|w\end{array}$ has the same number of $a\text{'}$s as $b\text{'}$s and $w$ has the

same number of $c\text{'}$s as $d\text{'}$s