To determine which operation is the top priority, follow PEMDAS. This means that those inside the Parenthesis are the top priority. This is followed by Exponents, Multiplication, Division, Addition and lastly, Subtraction.So,
15 − 4 + (7 − 5)2
15 - 4 + (2)(2)
15 - 4 + 4
15 - 0
15
Therefore, the answer is A.