Let $p, q, r$ and $s$ be distinct positive integers. Let $p, q$ be odd and $r, s$ be even. Consider the following statements :

1. $(p-r)^2(qs)$ is even.
2. $(q-s)q^2s$ is even.
3. $(q+r)^2(p+s)$ is odd.

Which of the statements given above are correct?