Walt listed the steps that occur during the formation of natural gas. plants and animals that live in a lake die. the dead plants and animals sink to the bottom of the lake. sand, dirt, and rocks bury the plants and animals. the dead plants and animals are exposed to extreme heat and pressure. within about twenty years, natural gas forms. which best describes walt’s mistake? only dead plants form natural gas. land plants and animals form natural gas. natural gas only requires extreme pressure to form. natural gas takes millions of years to form.

D. Natural gas takes millions of years to form.

The correct answer is option D which is, "Natural gas takes millions of years to form".

The Walt arrange all the steps correctly but his last step was not correct that natural gas takes only 20 years to form.

Natural gas, oil and coil are known as fossil fuels and they takes millions of years to be formed.

First dead material is converted into fossils due to high pressure and temperature, occurring many chemical reaction. Then natural gas is formed which is high volatile organic compounds formed from the fossils.

Hence the correct answer s option D.