Final answer:
Alcohol evaporators in air brake systems are used to help prevent moisture from freezing within the system.
Step-by-step explanation:
Alcohol evaporators are used in air brake systems of large vehicles, particularly in colder climates, to prevent moisture from freezing. Water in its liquid form is necessary for the proper functioning of air brake systems, but in freezing temperatures, the water can freeze and cause the brakes to fail. By adding alcohol, which has a much lower freezing point than water, alcohol evaporators reduce the likelihood that moisture will freeze within the system. The correct answer to the student's question is that alcohol evaporators may be used to c) help prevent moisture in the air brake system from freezing. By using alcohol evaporators, the alcohol can mix with the moisture and lower its freezing point, preventing it from freezing and ensuring the proper functioning of the air brake system.