In alphabet series, some alphabets are missing which are given in that order as one of the alternatives below it. Choose the correct alternative.
_ aaba _ bba _ bba _ abaa _ b
c _ bba _ cab _ ac _ ab _ ac
_ baa _ aab _ a _ a
_ abb _ _ bb _ a _ bbab _ ba
_ _ babbba _ a _ _
_ bc _ _ bb _ aabc