If x and y are positive integers, and 3x^2=3y, then which of the following must be a multiple of 9?
I. x^2
II. y^2
III. xy  Choose the correct choice from the following:	A) I only	B) II only	C) III only	D) I and II only	E) I, II and III
4x^2 = 3y   since x,y are positive integers, x^2 = x*x is divisible by 3 -&gt; x is divisible by 3 and y is divisible by x^2   -&gt; x^2 and y is divisible by 9 -&gt; y^2 is divisible by 9   (1),(2), and (3) must be true   I onlynswer is I only
<result>A</result>
If x and y are positive integers, and 3x^2=3y, then which of the following must be a multiple of 9?
I. x^2
II. y^2
III. xy