The correct answer is C. Resin, oil and turpentine.
Oil varnish is a transparent liquid that is applied to wood to protect it from the elements and to give it a glossy finish. It is made from a mixture of resin, oil, and turpentine. The resin provides the varnish with its strength and durability, the oil helps to bind the resin to the wood, and the turpentine helps to thin the varnish and make it easier to apply.
Option A is incorrect because synthetic resin is not a traditional ingredient in oil varnish. Option B is incorrect because wax is not a traditional ingredient in oil varnish. Option D is incorrect because spirit is not a traditional ingredient in oil varnish.