Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it?
abbab_b_bb_babb_bb

Correct option is A

Given: abbab_b_bb_babb_bb
From the given options-
(a) babb
Abb/ab bb/ abb bb/abb bbb (sequence followed)
(b) abab
Abb/ab ab bbb ababb_bb (sequence not followed)
(c) abbb
Abb/ab ab bbb bbabb_bb (sequence not followed)
(d) baba
Abb/ab bb/ abb bb/abb abb (sequence not followed)
Thus, the correct answer is (a).