In alphabet series, some alphabets are missing which are given in that order as one of the alternatives below it. Choose the correct alternative.
ab _ bc _ c _ ba _ c
ab _ bcbca _ _ c _ bab
ab _ aa _ bbb _ aaa _ bbba
ab _ aa _ caab _ c _ abb _ c
ab _ _ _ b_ bbaa _
_ abb _ _ bb _ a _ bbab _ ba