What must a motorcycle have if it carries a passenger?

A motorcycle that carries a passenger must be equipped with footrests for the passenger. This requirement is crucial for safety, as footrests provide a secure place for the passenger to position their feet, helping to maintain balance and stability while the motorcycle is in motion. Without designated footrests, passengers could inadvertently shift their weight in a way that destabilizes the motorcycle or leads to unsafe riding conditions.

In addition to the safety implications, proper footrests also ensure that the passenger is comfortable and secure during the ride. They help to keep the passenger's legs in a proper position, reducing the risk of their legs being caught in the wheels or in any moving parts of the motorcycle.

The other options do not establish necessary requirements for carrying a passenger on a motorcycle in South Carolina or may misrepresent the specific regulations. For instance, larger engines could provide more power but are not a legal requirement for carrying a passenger. Similarly, special sidecars are not mandatory for passenger transport, and while some registrations might occur in two-seat configurations, this does not directly pertain to the bike's outfitting for passengers.