Final answer:
When being passed by another vehicle, stay in your lane and maintain speed unless there's an emergency to ensure a safe and predictable passing scenario.
Step-by-step explanation:
When another vehicle is passing you, the correct response is to stay in your lane and maintain your speed unless there is an emergency. It's important to allow the vehicle to pass safely and not to create any unpredictable situations that might lead to an accident. Altering your speed by slowing down can sometimes be helpful if it allows the other vehicle to complete the pass more safely and quickly, but typically, maintaining speed is advised to provide a predictable scenario for overtaking vehicles.