Final answer:
It's safe to return to your lane when the car you've passed is visible in your rearview mirror, ensuring enough space for a safe lane change.
Step-by-step explanation:
When passing a car, it's safe to return to your original driving lane when you can see the front of the car you've passed in your rearview mirror. This ensures that you have enough space to merge back into the lane without cutting off the other driver or causing them to have to slow down. Always use your turn signals to indicate your intention to return to the lane, and make sure that you check your blind spots before moving over to confirm that another vehicle isn't in the lane you are moving into.