Decaying plants and animals are changed into oil and gas by A. wind B. water C. sunlight D. pressure

The answer is D. pressure

The correct answer is option D, pressure.

Fossil fuel is a usual term used for buried combustible geologic deposits of organic substances, produced from decayed animals and plants, which have been transformed to coal, crude oil, natural gas, or heavy oils by encountering with pressure and heat in the Earth's crust over hundreds of millions of years.

Or it can be said that Fossil fuels are the hydrocarbons, mainly fuel oil, coal, or natural gas, produced from the remains of the dead animals and plants.