The poem which is written in free verse is C. "Grass." Free verse refers to the fact that the poet doesn't follow any strict rules of poetry, such as those of rhyming schemes, or a perfect meter. B and D have regular rhymes, which is why they are incorrect. A doesn't have a rhyme, but has a regular meter where one line has 13 syllables, and the next one 11, and they alternate. The only poem which doesn't have the rhyme or a regular meter is "Grass."
