What does a yellow stop light indicate?

Answer: D — Caution

A yellow stop light requires you to slow down and prepare to stop your vehicle. It is not necessary to immediately stop when the light turns yellow, but you should not speed up either. Option A is incorrect because you should never speed up when you see a yellow light. Option B is incorrect because stopping immediately on a yellow light can cause accidents. Option C is incorrect because yielding is not required on a yellow light, but on a red light. Therefore, D is the correct answer as it signals caution and a need to slow down.