The correct answer is C. Oil reservoir.
An oil reservoir is a subsurface pool of hydrocarbons (liquid petroleum and natural gas) that is contained by a rock formation. The rock formation is typically porous and permeable, allowing the hydrocarbons to flow through it. The hydrocarbons are trapped in the reservoir by a cap rock, which is a layer of impermeable rock that prevents them from escaping.
An oil trap is a geological structure that traps hydrocarbons. The trap can be formed by a variety of mechanisms, including folding, faulting, and erosion. The most common type of oil trap is a structural trap, which is formed by the folding of sedimentary rocks.
A source bed is a rock formation that contains the organic material that is converted into hydrocarbons. The organic material is typically derived from the remains of plants and animals that lived in the past. The source bed must be buried deep enough and under the right conditions for the organic material to be converted into hydrocarbons.
None of these is the correct answer.