A very small fraction of the mass of plants and animals that have died during the last few hundred million years has been buried without decaying, and the heat and pressure deep within the earth have changed some of the stored solar energy in their bodies into coal, oil, and gas.
(plants and animals; have died; T:during the last few hundred million years) (A very small fraction of the mass of plants and animals; has been buried; ) (the heat and pressure deep within the earth; have changed; some of the stored solar energy; into coal, oil, and gas)
plants and animals A very small fraction of the mass of plants and animals the heat and pressure deep within the earth
have died has been buried have changed
T:during the last few hundred million years
some of the stored solar energy into coal, oil, and gas