The correct answer is option 4, Kerosene.

Option 1, Gum, refers to tree sap which is collected and used for various purposes. Option 2, Plywood, is a wood product made from thin layers of wood veneer. Option 3, Sealing wax, is a product made from resins extracted from trees.

However, option 4, Kerosene, is not a forest product. Kerosene is a fossil fuel derived from crude oil, which is found in underground deposits formed from the remains of ancient plants and animals. It is not directly obtained from trees or forests.

Therefore, the correct answer is option 4, as it is the only option that is not derived from a forest or tree source.