Final answer:
The courteous action when approaching an emerging car on the freeway is to slow down and allow it to merge into the traffic safely.
Step-by-step explanation:
When driving onto the freeway, the common courtesy to follow when approaching an emerging car is to slow down and let the emerging car merge into the traffic. Other options like speeding up to pass the emerging car quickly, honking the horn, or ignoring the emerging car are not considered courteous or safe driving practices.
It is important to facilitate a smooth integration of vehicles into the flow of traffic to maintain safety and reduce the risk of accidents. By slowing down, you allow the merging vehicle the space and time it needs to enter the freeway seamlessly.