Which of the following groups of letters when sequentially placed from left to right will complete the given series?
aaaa_bbbbbaaaa_bbbbb_aa_abbbbbaaaaabbbbb

Correct option is B

Given: aaaa_bbbbbaaaa_bbbbb_aa_abbbbbaaaaabbbbb
From the given options: -
(a) bbaa
aaaa/ bbbbbb/aaaa/ bbbbbb/ aaa aa/bbbbbaaaaabbbbb (Sequence not followed)
(b) aaaa
Aaaa a/bbbbb/aaaa a/bbbbb/ aaa aa/bbbbb/aaaaa/bbbbb (Sequence followed)
(c) abab
aaaa a/bbbbb/aaaa/ bbbbbb aaa babbbbbaaaaabbbbb (Sequence not followed)
(d) bbbb
aaaa/ bbbbbb/aaaa/ bbbbbb b/aa babbbbbaaaaabbbbb (Sequence not followed)