If you are going to overtake and pass another vehicle you should:

Answer: C — Ensure that the vehicle is not making a turn

When attempting to overtake and pass another vehicle, it is important to ensure that the vehicle ahead is not making a turn. Option A, turning on your headlights, is not necessary for overtaking and passing another vehicle. Option B, not exceeding the speed limit, is important to follow at all times but does not specifically apply to overtaking. Option D, sounding your horn, is not necessary and could potentially startle the driver ahead, causing a potential accident. Therefore, option C is the most appropriate and safe choice when overtaking and passing another vehicle.