In alphabet series, some alphabets are missing which are given in that order as one of the alternatives below it. Choose the correct alternative.
_ aba _ cabc _ dcba _ bab _ a
abb _ baa _ a _ bab _ aba
_ _ aba _ _ ba _ ab
ac _ cab _ baca _ aba _ acac
ab _ bcbca _ _ c _ bab
_ _ babbba _ a _ _