ANS:A - remove oil vapour or moisture from air.

'End cooler' or 'after cooler' in an air compressor is employed mainly to: remove oil vapor or moisture from air. After compression, the air in the compressor contains high levels of heat, which can cause moisture or oil vapor to condense. The end cooler, also known as an after cooler, cools down the compressed air, causing the moisture and oil vapor to condense into liquid form. This condensed moisture and oil can then be removed from the compressed air before it is used in applications where dry, clean air is required. By removing moisture and oil vapor, the end cooler helps to prevent damage to downstream equipment, ensures the quality of the compressed air, and reduces the risk of corrosion or contamination in pneumatic systems. Therefore, it plays a crucial role in maintaining the efficiency and reliability of air compressor systems.