For which values of x is the expression (x²-4)/(x²-2x) undefined?

An expression is undefined where its denominator equals zero. Factor the denominator: $x^2 - 2x = x(x - 2)$, which is zero when $x = 0$ or $x = 2$. That makes the answer D. Although the numerator $x^2 - 4 = (x-2)(x+2)$ shares the factor $x - 2$ with the denominator, canceling would hide the problem at $x = 2$, but the original expression is still undefined there. Choice A misses $x = 0$. Choice B uses the zeros of the numerator, $\pm 2$, which are where the expression equals zero (or is a hole) and not where it is undefined. Choice C misses $x = 2$.