For which values of $x$ and $y$ does $(xy)²$ equal $x² y²$? For which values of $x$ and $y$ does $(xy)²$ not equal $x² y²$?

a) $x = 0, y = \text{any value}$
b) $x = 1, y = \text{any value}$
c) $x = \text{any value}, y = 1$
d) $x = \text{any value}, y = 0$