The correct answer is option 4: Hydrogenation. Hydrogenation is the process of adding hydrogen to vegetable oils to convert them into solid fats, such as ghee. During this process, the unsaturated fatty acids present in the vegetable oils react with hydrogen gas in the presence of a catalyst, resulting in the conversion of the double bonds in the fatty acids into single bonds. This process increases the melting point of the oil, making it solid at room temperature. The hydrogenation process allows for the production of solid fats, such as ghee, which have a longer shelf life and are more stable for cooking and baking purposes. It is important to note that hydrogenation can also lead to the formation of trans fats, which have been associated with various health risks.