Why Is Oil Not Degraded When in a Natural Habitat

Why is oil not degraded when in a natural habitat underground, yet susceptible to bioremediation in an oil spill?

A) The high pressure the oil is subjected to underground prevents bacteria from growing and consuming it.
B) The bacteria can't be given the right amounts or types of nutrients to foster an increase in their number deep underground. Nearer the surface, human intervention can increase the factors that will raise the microbe quantity.
C) The bacteria that degrade the oil require a higher than normal salt content, much like what is found in seawater. Underground, they lack this salt level.
D) It IS degraded underground-but it happens at a much slower rate because a portion of the cycle is photosynthetic in nature. This process is dramatically increased nearer to the water's surface.