Black tea describes the most popular variety of tea in the United States. It is made by deliberately exposing the leaves of Camellia sinensis to oxygen before preserving them by roasting, baking, or frying. This sustained oxidation produces leaves that are dark brown to black in color, and a liquor that is red to golden. Black tea preserves its flavor longer than other teas and for this reason it has been the favorite tea of regions, such as Europe and North America, which are far removed from the countries, such as India and China, in which tea is cultivated. Unlike most tea varieties, black tea is always prepared with boiling water. The finest black tea is produced in the Chinese province of Yunnan, in Sri Lanka, and in the Darjeeling, Assam, and Putharjhora regions of India.