Final answer:
When another vehicle is passing on the left, you should maintain your speed, stay in your lane, and ensure you do not drift into the other lane or make sudden moves that could endanger both vehicles.
Step-by-step explanation:
If another vehicle is passing you on the left, the appropriate action is not to stop or become stationary but rather to maintain your speed and stay in your lane, ensuring that you don't interrupt the flow of traffic or create a potential hazard. Therefore, options a, b, and c are not applicable. It is also important to ensure that your vehicle does not drift into the adjacent lane and that you abstain from any sudden maneuvers that might endanger both yourself and the other driver. In general, remaining aware of your surroundings and exhibiting courteous driving behavior is critical when another vehicle is passing you on the left.