Question

Which is a characteristic of free verse poetry?

Answer 1

The answer is No rhyme scheme as that would transform it into Rhyme Poem Type

Answer 2

I believe the answer would be no rhyme scheme. 
Free verse poems are poems that are pretty much self explanatory. It is in the name, free verse, meaning that these poems do not follow any set of particular poetry rules/guidelines, nor do they have any rhythm/rhyme scheme. 

Therefore, the answer is the last answer option.
Hope this helps!