The Purple Cow
(Reflections on a Mythic Beast Who's Quite Remarkable, at Least.)

I never saw a Purple Cow;
I never hope to See One;
But I can Tell you, Anyhow,
I'd rather See than Be One.

What is the main difference between “The Purple Cow” and Frost’s poem "Mending Wall"?

the use of rhyming in “The Purple Cow”
the use of rhyming in “Mending Wall”
the use of free verse in “Mending Wall”
the use of iambic pentameter in “The Purple Cow”