What is a critical step to follow at the end of each workday concerning air tanks?

Answer: C — Drain the air tanks

Draining the air tanks at the end of each workday is essential because it removes any accumulated moisture and contaminants that can lead to various issues. Over time, moisture in the air system can create ice during cold temperatures and corrode the internal components, reducing the effectiveness and longevity of the braking system. Proper maintenance, including draining the air tanks, helps to ensure that the air brakes function optimally, which is critical for safety on the road. This practice is part of routine vehicle maintenance that directly impacts vehicle performance and safety, making it a necessary step for commercial drivers to follow.