What could prevent air pressure from building up in an air-brake system in frosty weather? What could prevent air pressure from building up in an air-brake system in frosty weather?

• Possible answers:

   
• A. Moisture in the air may form bubbles in the brake fluid
• B. The air will contract, reducing the pressure
• C. The dampness may cause valves to rust
• D. Moisture drawn in with the air may freeze and cause a blockage