Not Regular language [find out]

Question

 

Why is C is regular as it non regular as?

Please help me with  this confusion

Comments

There’s already plenty of explanations about this.

Answer 1

C) It is actually starting with 2 same symbols and ending with their reverse 

you can easily make NFA using Binary Tree like structure

here is Regular Expression for the same :

aa Σ* aa + ab Σ* ba + bb Σ* bb + ba Σ* ab