Select the option that represents the letters that, when sequentially placed from left to right in the blanks below, will complete the letter series.

d _ c d _ b _ d _ c d c _ d d b c _c b d

b c d b b d

By observing all options , We find that only option 3 fits well to form a repeated series .

d _ c d _ b _ d _ c d c _ d d b c _c b d