Where is crude oil predominantly found?

Crude oil is predominantly found in rocks, specifically in sedimentary rock formations beneath the Earth's surface. These rocks act as reservoirs for oil deposits, allowing for the accumulation and trapping of organic materials that eventually convert into crude oil over millions of years. The geological conditions needed for oil formation typically involve the presence of source rocks containing organic matter, followed by the right temperature and pressure over geological time to facilitate the transformation into hydrocarbons.

While it may be possible for small amounts of oil to be present on the surface or in ocean waters due to leaks or spills, large and extractable reserves are primarily found within the porous structures of sedimentary rocks underground. This understanding underscores why this option correctly identifies the primary location of crude oil reserves.