Task: Question Answering
Input (English): If \(c\) and \(d\) are integers and \(c^2 - d^2\) is even, which of the following must be true?
(A)\(cd\) is odd (B)\(cd\) is even (C)\(c + d\) is odd (D)\(c + d\) is even (E)\(c - d\) is odd
Output (English): D