What is the recommended method to fasten cargo to a motorcycle?

Answer: C — Secure with elastic ropes

Using duct tape is not recommended as it can potentially damage the surface of the motorcycle and may not hold the cargo securely. Tying items loosely with thread is not a strong enough fastening method and can easily become undone during the ride. Leaving items loose on the seat can be dangerous as they can fall off and potentially cause accidents. The recommended method is to secure the cargo with elastic ropes as they provide a stable and secure fastening without damaging the surface of the motorcycle.