The correct answer is A) the use of rhyming in the “Purple Cow.”
The main difference between the “Purple Cow” and Frost’s poem “Mending Wall” is the use of rhyming in the “Purple Cow.”
The “Mending Wall” uses no rhyming in its lines, meanwhile “The Purple Cow” indeed uses rhyming in alternative lines. That is the main difference. American writer Gelett Burgess wrote the poem “Purple Cow” in 1895. It was published in the author’s magazine called “The Lark.”
The other options of the question were b) the use of rhyming in the “Mending Wall,” c) the use of free verse in the “Mending Wall,” and d) the use of iambic pentameter in the “Purple Cow.”