ITMC 2018 Grade 7 National Preliminary set01 Question 24

Question 24

A perfect square is the square of an integer: $N=n^2$. Suppose $N$ is a perfect square, $x,y$ are integers, $\gcd(x,y)=1$, and $N=xy$. Which statement is always true?

Both x and y are perfect squares
Exactly one of x and y is a perfect square
x+y is a perfect square
The positive difference of x and y is a perfect square
None of these