GCSE Maths Practice: algebraic-proof

\( \text{Prove that the sum of an even and odd number is always odd. Which expression is correct?} \)

Choose one option:

\( n + m = 2(k - l) + 1 \) \( n + m = 2(k + l) + 1 \) \( n + m = 2(k + l) - 1 \) \( n + m = 2(k + l) \)