Final answer:
The ownership of the oil discovered on a rancher's land depends on jurisdictional laws and existing agreements or contracts. The state government or federal government may own the oil if laws grant them ownership over natural resources found on privately owned land.
Step-by-step explanation:
In the scenario where a rancher owns a parcel of land on which oil is discovered and has not previously conveyed the oil rights, the ownership of the oil would typically depend on the jurisdiction's laws regarding mineral rights.
Option C, the state government, or Option D, the federal government, could potentially own the oil if the laws grant them ownership over natural resources found on privately owned land.
The ownership of the oil could also vary depending on any existing agreements or contracts between the rancher and other parties involved, such as lease agreements or prior conveyances of oil rights.