Explanation:

- Option 1: Allicin

- Correct Answer.

- Allicin is a sulfur-containing compound found in garlic and to a lesser extent in onions. It is responsible for the distinctive smell and has various health benefits.

- Option 2: Cellulose

- A complex carbohydrate not related to sulfur.

- Found in the cell walls of plants, it provides structural support but is not an active compound in garlic or onion.

- Option 3: Ethanol

- A type of alcohol not related to sulfur.

- Commonly known for its presence in alcoholic beverages and not typically associated with garlic or onion.

- Option 4: Phenol

- An organic compound that doesn't contain sulfur.

- Known for its role in some disinfectant activities but not a main component in garlic or onion.