Final answer:
If an ambulance is approaching, you should stop your vehicle and remain stationary, not drive on the shoulder to pass unless it's an emergency or you're instructed by authorities.
Step-by-step explanation:
You asked, "Do not drive on the shoulder to pass except during an emergency or when directed by authorities." The correct response to situations involving an emergency vehicle, like an ambulance, would be option (a): Stop moving and become stationary till it passes by. It's important not to drive on the shoulder to overtake vehicles unless there's an emergency situation or you are instructed to do so by law enforcement or other authorities. The shoulder of the road is primarily for emergencies, stopping when a vehicle is in distress, or for the use of emergency vehicles. Always follow traffic laws and respect signals from authorities to ensure safety on the road.