The correct choice is (c) per % nos
Best explanation: In a large industrial brickworks, clay is taken from the quarry, and then carried by conveyor belt or truck/lorry to the main factory, although it may be stockpiled outside before entering the machinery. When the clay enters the preparation plant (Clay Prep) it is crushed, and mixed with water and other additives which may include breeze, a very fine anthracite that aids firing. This process, which is also known as pugmilling, improves the consistency, firing qualities, texture, and colour of the brick. From here, the processed clay can be extruded into a continuous strip and cut with wires, or put into moulds or presses (also referred to as forming) to form the clay into its final shape. After the forming or cutting, the bricks must be dried, either in the open air, in drying sheds, or in special drying kilns. When the bricks have been dried, they must then be fired or ‘burnt’ in a kiln, to give them their final hardness and appearance.