Choice A is the correct answer.

1. Check first term: $x^2$.
2. Check last term: $25 = (-5)^2$.
3. Check middle term: $2(x)(-5) = -10x$.

This is a perfect square trinomial matching $(a-b)^2$. Thus, $(x - 5)^2$.

Choice B is incorrect because the middle term would be positive. Choice C is incorrect because this is a difference of squares ($x^2 - 25$). Choice D is incorrect because the constant would be 100.