What is a common feature of high-quality slack adjusters?

Answer: B — They automatically adjust as brakes wear

High-quality slack adjusters are designed to automatically adjust as brakes wear down. This feature is essential for maintaining optimal brake performance without requiring frequent manual intervention. Automatic adjustment helps ensure that the brake shoes remain in proper contact with the brake drums, which leads to effective stopping power and enhanced safety on the road. In contrast, slack adjusters that require constant manual adjustment can be more labor-intensive and may lead to inconsistent brake performance if not monitored properly. Options that reference materials or noise characteristics like being made entirely of plastic or being quieter than standard adjusters do not directly relate to the essential functionality and performance benefits of high-quality slack adjusters. Their critical feature lies in their ability to self-adjust, ensuring reliability and efficiency in the braking system.