Which of the following expressions can be factorised using the difference of squares identity?

Correct answer: \(x^2-25\)

Answer: A, \(x^2-25\). The difference-of-squares identity is \(a^2-b^2=(a-b)(a+b)\). Its two requirements are: both terms must be perfect squares, and they must be separated by a minus sign. Here \(x^2=x^2\) and \(25=5^2\), so \(x^2-25=x^2-5^2=(x-5)(x+5)\). Option A therefore fits exactly. Option B is a sum of squares, not a difference of squares. Option C is a perfect-square trinomial, \((x+5)^2\), so it uses a different identity. Option D is also a perfect-square trinomial, \((x-5)^2\), not a difference of two squares in the required two-term form. Memory cue: look for “square minus square”; the factors always have one minus and one plus sign.