Step 1: Role of hydrogen in preparing Vanaspati Ghee.
Vanaspati Ghee is prepared through a process called hydrogenation. In this process, hydrogen gas is bubbled through liquid vegetable oils in the presence of a nickel catalyst. This converts unsaturated fatty acids into saturated fatty acids, resulting in a semi-solid product.
Step 2: Explanation of other options.
Option (A): Olive oil. Incorrect. Olive oil is a liquid vegetable oil and is not hydrogenated.
Option (B): Ghee. Incorrect. Ghee is prepared from animal milk fat, not through hydrogenation.
Option (C): Coconut oil. Incorrect. Coconut oil is a natural saturated fat and does not require hydrogenation.
Step 3: Conclusion.
Hydrogen is used in the hydrogenation process to prepare Vanaspati Ghee.
\[
\therefore \text{The correct answer is: Vanaspati Ghee.}
\]