Let A = {ww | w {a, b, c} }.

Suppose you are trying to prove that A is not a context-free language using the context-free language pumping lemma. Your proof starts (correctly) like this:

Suppose for a contradiction that A is a context-free language. Let p be the pumping length given by the pumping lemma.

Now you have to choose string s. For each choice of s below, state whether or not this choice of s can be used to finish the proof that A is not a context-free language. If your answer is YES you do not have to explain anything. If your answer is NO, you should also briefly explain why it can not be used.