Choice C is the correct answer. The discriminant $\Delta = b^2 - 4ac$ determines the nature of the roots.

• If $\Delta > 0$, there are two distinct real solutions.
• If $\Delta = 0$, there is exactly one real solution (repeated).
• If $\Delta < 0$ (negative), there are no real solutions (two complex imaginary solutions).

Choice A is incorrect because that requires $\Delta > 0$. Choice B is incorrect because that requires $\Delta = 0$. Choice D is incorrect because quadratics have at most 2 solutions.