How should motorcycle brake fluid be replaced?

Answer: B — By bleeding the brake lines to remove old fluid and air bubbles

Replacing motorcycle brake fluid involves an important procedure to ensure the brake system functions safely and effectively. The correct method entails bleeding the brake lines to remove old fluid and any air bubbles that may have entered the system. Brake fluid can degrade over time, absorbing moisture and losing its effectiveness. Additionally, any air trapped in the brake lines can impede the braking system's performance, leading to a soft or unresponsive brake feel. By properly bleeding the brake lines, old fluid is pushed out, and new fluid is introduced, ensuring a clean system that maintains optimal brake performance. The other methods mentioned would not adequately address the needs of the brake system. Simply draining the reservoir may not eliminate all the old fluid present in the lines. The top-off method might lead to a mixture of old and new fluid, which won't fully refresh the system, while replacing the calipers entirely is an excessive measure when the fluid change alone is required for safe and effective braking.