Perfecr square means \(x^2\) where x is an integer.
So, it is easy to see on each answer.
Note: not necessarily means either a perfect square or not.
Let assume \(x=a^2\) and \(y=b^2\), where a and b are integers.
(A)\(x^2=a^4\), so, a perfect square
(B)\(xy=a^2b^2=(ab)^2\), so, a perfect square
(C)\(4x=4a^2=(2a)^2\), so, a perfect square
(D)\(x+y=a^2+b^2\). Not necessarily a perfect square. See your own example.
(E)\(x^5=a^10=(a^5)^2\), so, a perfect square.
All in all, the answer is (D)
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