Correct Answer: tmhmtlm

Solution : Given:
h_t_l_tt_lht_m_htt_l

To fill the series we have to divide the series – h_t_ l /_tt _l / ht _m_ / htt_l
Let's check each option –
First option: hmmttlm; h h t m l / m tt t l / ht t m l / htt m l (No repeated pattern has been found.)
Second option: tmhmtlm; h t t m l / h tt m l / ht t m l / htt m l (httml is repeated in the series.)
Third option: lmtmhmt; h l t m m / t tt m l / ht h m m / htt t l (No repeated pattern has been found.)
Fourth option: mmhtltm; h m t m m / h tt t l / ht l m t / htt m l (No repeated pattern has been found.)

So the series is httmlhttmlhttmlhttmlhttml. Hence, the second option i s correct.