The correct answer is C. Commutative Property
I don't really understand it that much either but I think that the answer is A cause a rectangle has two small sides and two longer sides sooo hope this helps :D
Use exp/log functions to rewrite y as

One of the properties of logarithms lets us bring down the exponent, so

Now take the derivative of both sides with respect to x. By the chain and quotient rules,

Simplify:

6/8. multiply 3/4 by 2 and there is your answer.