In alphabet series, some alphabets are missing which are given in that order as one of the alternatives below it. Choose the correct alternative.
_ bcdbc _ dcabd _ bcdbc _ dc _ bd
_ _ babbba _ a _ _
_ aba _ cabc _ dcba _ bab _ a
_ bbca _ bcca _ ac _ a _ cb
_ baa _ aab _ a _ a
_ bc _ _ bb _ aabc