Which of the following steps was necessary for the formation of all fossil fuels?

the remains of plants and animals are buried at the bottom of oceans.

carbon bonds break, producing methane gas.

heat and pressure build up on top of decaying matter.

the remains of plants and animals are buried at the bottom of swamps.

Heat and pressure build up on top of decaying matter was necessary for the formation of all fossil fuels.

Explanation:

Fossil fuels are different energy sources in the form of hydrocarbons, which come from older geological periods, and which can be found on or below the ground in the litho and pedosphere. According to the biogenic theory, which prevails today, the fossil fuels are the remains of ancient animals and plants that have been buried in the earth and then decomposed under high pressure and heat to their constituents (mainly carbon and carbon compounds).

The fossil fuels mainly comprise natural gas, petroleum and coal. Natural gas consists mainly of the gas methane and has a high content of the element hydrogen compared to the element carbon. Methane is found in natural gas fields together with crude oil or bound as methane clathrate. Petroleum (also called crude oil) is found in liquid form and contains a larger amount of the elemental carbon, while the non-volatile rock species also called carbon (not to be confused with the elemental carbon) contains a very large amount of the elemental carbon. Anthracite consists almost of pure carbon. All of these fuels are very important for trade. There are also other fossil fuels that are largely untapped, such as oil shale, various sedimentary rocks containing hydrocarbons.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.