The correct answer is C. 25 to 30 years.
Creosote oil is a wood preservative that is used to protect wood from decay and insect damage. It is a dark brown or black liquid that is made from coal tar. Creosote oil is applied to wood by dipping, spraying, or brushing. It can also be applied to wood in the form of a paste or a liquid.
Creosote oil is a very effective wood preservative. It can protect wood from decay and insect damage for many years. The life of creosote-treated wood depends on a number of factors, including the type of wood, the climate, and the level of exposure to moisture and insects. In general, creosote-treated wood can last for 25 to 30 years.
Option A is incorrect because creosote-treated wood can last for much longer than 5 years.
Option B is incorrect because creosote-treated wood can last for much longer than 15 years.
Option D is incorrect because creosote-treated wood can last for much shorter than 60 to 70 years.