Answer:
2
Explanation:
A perfect square is the product of a number multiplied by itself.
So, 9 would be 3 x 3 so that's a perfect square.
1 is 1 x 1, so that is a perfect square.
4 is 2x2, so that is a perfect square.
2 does not have a number that multiplies by itself to equal 2, so it is not a perfect square.