When stopped at a red light, a driver must not proceed until...?

Answer: C — The light has changed to green and the intersection is clear

Drivers must not proceed at a red light until the light has changed to green and the intersection is clear. Option A is incorrect because it only mentions the light turning green, but does not consider whether the intersection is clear. Option B is also incorrect because it only mentions the intersection being clear, but does not consider the state of the traffic signal. Option D is incorrect because it suggests a specific time requirement, whereas the correct answer states the specific conditions that must be met before proceeding at a red light.