Explanation:

- Option 1: Cellulose ??

- Viscose is indeed obtained from cellulose, usually sourced from wood pulp.

- This makes it a semi-synthetic fiber, as it comes from a natural source.

- Cellulose undergoes a chemical process to become viscose, a common material in fabrics.

- Option 2: Oil

- Oil is the basis for synthetic fibers like polyester.

- Viscose is not derived from oil.

- Option 3: Petrochemicals

- These are used to make fibers like nylon and polyester.

- Viscose comes from natural cellulose, not petrochemicals.

- Option 4: Coal

- Coal is not used in producing viscose fiber.

- Coal was historically used in synthetic fiber but not for viscose.