Correct Option: C

Generally, there are four different tea categories that differ in processing methods. By withering, new picked leaves are thinly spread to dry during this process. Heated air is forced over the leaves if the climate is not suitable. The main goal of this process is to reduce the water content. By the end of withering, the leaves should be pliable enough to be rolled. From the withering racks, the leaves are now twisted and rolled so that the leaf cells are broken up. Oxidation is a bio-chemical process where oxygen is absorbed. It begins once the leaf membranes are broken during the rolling process. Oxidation causes the leaves to turn bright copper in colour. During the stage of drying or firing, the leaves are dried evenly and thoroughly without being burnt. Firing the leaves stops the oxidation process.