Select the combination of letters that when sequentially placed in the blanks of the given letter series will complete the series. a_ _dda_ _cb_ _ _cac_ _da_

cbcaddabdc bddaccbbdd bddacbdcbd bdddcbdacc

cbcaddabdc

a c b d d a c / a c b d d a c / a c b d d a c c b c a d d a b d c