Which of the following is not a safety feature on a motorcycle?

The muffler is primarily designed to reduce noise produced by the motorcycle’s engine and does not contribute directly to safety in the same way that other motorcycle components do. Safety features are typically those that enhance the rider's visibility, communication with other road users, or alertness to potential hazards.

The horn, headlights, and turn signals all serve important safety functions. The horn allows the rider to sound an alert to warn other drivers of their presence, especially in situations where visibility may be compromised. The headlight improves visibility during low-light conditions and also makes the motorcycle more visible to other road users during the day. Turn signals are crucial for communicating the rider's intentions to others on the road, helping to prevent accidents by signaling turns or lane changes. Thus, while the muffler is important for noise control and engine performance, it does not provide a direct safety benefit.