Final answer:
If preparing to turn left and seeing an oncoming vehicle, one should stop and wait until the vehicle passes to avoid a collision, prioritizing road safety.
Step-by-step explanation:
If you are prepared to turn left at an intersection and notice an oncoming vehicle, the appropriate action to take is to stop moving and become stationary until the vehicle has passed by. This is a critical aspect of road safety, ensuring that you avoid a potential collision. Making a left turn in front of an approaching vehicle can lead to a serious accident if there isn't enough distance or the oncoming vehicle is moving too quickly to safely make the turn. Your priority should always be to ensure the safety of all road users by exercising patience and proper judgment when turning at an intersection.