Which sentence is correctly punctuated?

Nope. Please try again. Think about interrupting phrases and how they are punctuated.

If we move the prepositional phrase to the front, we get In my opinion, this test is easy. Thus, where do the commas go?

That is incorrect. The correct answer is A) "This test, in my opinion, is easy."

To determine the correct punctuation, we need to identify the nonessential clause in the sentence, which is "in my opinion." This clause provides additional information but is not necessary for the main meaning of the sentence. Nonessential clauses are usually enclosed by commas.

In option A, there are commas placed before and after the nonessential clause, which correctly separates it from the rest of the sentence. Therefore, option A is correctly punctuated.