The best answer for this question is "free verse." This poem does not follow any particular rhyme scheme or stanza patterns. This rules out the second option and part of the last option. It also does not contain any internal rhythms, including iambic pentameter. This rules out the first and last options, leaving you with only one. Whitman was notorious for writing in a very free flowing way that defied norms and traditions of poetry. Hope this helps.
