What must you remember with an air brake system with air-drier?

You answered correctly. For vehicles with an air brake system that includes an air-drier, it is important to regularly check the water-drainage valves of the air tanks to ensure the drier is functioning and to service the air-drier according to the maintenance schedule. This is because the air-drier is responsible for removing moisture from the compressed air, which prevents corrosion and freezing in the brake system. Regular checks and servicing help maintain reliable brake performance. Checking the antifreeze level is not required for a typical air-drier, so answer 3 is not necessary. This way, you ensure both the air-drier and braking system work safely and efficiently.