Which of the following is a common risk factor for motorcycle accidents?

Answer: C — Driving under the influence of alcohol

Driving under the influence of alcohol is a significant risk factor for motorcycle accidents because alcohol impairs a rider's judgment, coordination, and reaction times. When a rider's cognitive functions are compromised, they are less able to assess road conditions, respond to hazards, or make quick decisions that are crucial for safe riding. This impairment increases the likelihood of an accident, making it a critical factor in motorcycle safety. In contrast, riding with a full tank of gas is not inherently dangerous and does not directly contribute to accidents. Following traffic rules diligently is essential for safety and can actually reduce the risk of accidents. Similarly, wearing protective gear is a safety measure that helps reduce the severity of injuries in case of an accident, thus also serving to enhance safety rather than increase risk.