What equipment is essential for bicycle passengers?

Answer: D — Proper seat and protective equipment

The essential equipment for bicycle passengers includes a proper seat and protective equipment to ensure their safety during the ride. Having a designated passenger seat ensures that the passenger can sit securely without affecting the rider's balance or control of the bike. Protective gear, such as helmets and pads, is crucial for minimizing the risk of injury in the event of a fall or collision. This equipment helps to comply with safety regulations and promotes safe riding practices. While other options mention various aspects of passenger safety, they either suggest non-essential components or do not fully address the necessary protections for bicycle passengers. The inclusion of both a proper seat and protective equipment covers the foundational safety requirements for anyone riding as a passenger on a bicycle.