I believe B is a right answer, first is out because we don't know the value of y and we can't say that the squares of primes 2,3,5 will be factors of y for any possible value of y. So, only probable values of x can be 2,3, and 5. 5 can be omitted because it's not a factor of 36. Now, it's seen that squares of both primes (2 and 3) are factors of 36. Therefore, for any possible value of x^2, x^2 is a factor of y.
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