It’s actually D.
You have to look at both x and y and it’s power. You have to look for the lowest power for x and y. For y as you can see that the lowest power is 2. As for x it can be either power of 3 or even 2. When you removed x^2 and y^2 from the equation. The inside parenthesis will be x^2-3xy. Just remember when you divide both x^2 and y^2, you subtract the power.
When you get the answer, please check the answer if it’s the same as the original. Meaning distribution both x^2 and y^2 to inside parenthesis. And for the power, you add them. This way you can double check and see if it’s the same.