The answer is D. AABB.
"Roar" is the first rhyme so we call itA. Since "core" rhymes with it, you add another A next to it. And because "bleat" does not rhyme with those two words, you add the next letter of the alphabet, B. And because "sweet" rhymes with it, we add another B. In conclusion, the rhyme scheme would be "AABB".
I hope this is helpful! :D