Partial hydrogenation of vegetable oils involves adding hydrogen to unsaturated fats in the presence of a nickel catalyst at high temperatures. This process converts some of the double bonds in the unsaturated fats into single bonds, making the fats more solid and stable. Butter is a dairy product made from cream or milk and is not produced by hydrogenation. Vanaspati ghee is typically made by fully hydrogenating vegetable oils, not partial hydrogenation. Cheese is a dairy product unrelated to hydrogenation. Margarine, on the other hand, is produced by partial hydrogenation of vegetable oils, making it the correct answer.
Conclusion: The correct answer is (D) Margarine.