While preparing tea, Rehan filters out tea leaves from the liquid with a strainer. The process used in this situation is
Separation
A separation process is a method to achieve any phenomenon that converts a mixture of chemical substances into two or more distinct product mixtures, which may be referred to as mixture, at least one of which is enriched in one or more of the mixture's constituents. Filtering out tea leaves from liquid results in separation of constituents of tea. Hence, this process is separation.