When using the pumping lemma with length to prove that the language L $=\{$anban$,$ n$>0\}$ is nonregular, the following approach is taken.

Assume L is regular.

Then there exists an FA with k states which accepts L$.$

We choose any word w which is a word in L$.$

Which one of the following would be an appropriate word w$?$

$1.$

ambam for m$>0$

$2.$

akbak

$3.$

a$100$ba$100$

$4.$

akbkak