The most accurate description of what must have happened in an area with a large petroleum trap is:
B.) organic matter must have been buried and placed under intensity and pressure until it became petroleum then the petroleum mass connected inside and in impermeable underground rock formations.
This option correctly outlines the process of formation of petroleum, which involves the burial of organic matter (like plants and animals) over millions of years, subjecting it to heat and pressure to transform it into petroleum, followed by the accumulation of petroleum in reservoirs that are typically trapped by impermeable rock formations.