Which function has only one x-intercept at (−6, 0)?

An x-intercept occurs where f(x) = 0. In choice D, f(x) = (x + 6)(x + 6), so the only zero is x = −6; the repeated factor gives the single intercept (−6, 0). The other choices have zeros at different values or have an intercept at x = 6.

AI-written and checked against the verified answer.