While driving at the speed limit on an 80 km/h multi-lane highway, what must you do if a car approaches from behind?

When driving on a multi-lane highway, it's important to adhere to the principles of maintaining a smooth flow of traffic. If a car approaches from behind while you are driving at the speed limit, the best course of action is to change lanes to the right when safe to do so. This allows the vehicle behind you to pass without having to adjust their speed significantly, which helps avoid potential frustrations and keeps traffic moving efficiently.

Changing lanes to the right is courteous and promotes safety on the road by allowing faster vehicles to proceed unhindered. It also contributes to better traffic flow, as it enables both vehicles to continue at their respective speeds without unnecessary hindrance.