What is the primary cause of brake fade on a motorcycle, and how should a rider address it?

1. Overheating of brake components due to excessive continuous use; downshift to use engine braking and let the brakes cool
2. Air bubbles in the brake lines; pump the brakes as hard as possible
3. Contamination of the brake pads with road salt; spray them with water while riding
4. Worn tire tread; replace the tires immediately