Remember in PEMDAS (P = Parenthesis, E = Exponent, M = Multiplication, D=Division, A= Addition, S= Subtraction), you always do the Parenthesis or Brackets first. So your equation will become 5 x 5 in the end. Therefore the answer is "C) product".
I believe this would be the product because you are multiplying. The sum would mean addition, the quotient is the answer to a division problem and the difference would be subtraction!