many people try to eliminate fat from their diets. which is one reason it is
necessary for humans to eat fat?

Fats are  composed of Fattyacid. some fatty acids such as icosapentanoic acid(EPA) and Docosohexanoic acid(DHA) are omega 3 fatty acids which are very much important in brain development and also reduces the risk of coronary artery disease.

Explanation:

Accumulation of excess fat leads to generation of obesity and other health disorders such as risk of heart disease and fatty liver.

               But all fats are not bad for example High Density Lipoprotein helps in the transport of cholesterol from the peripheral tissue to liver thus reducing the rick of atherosclerosis.

                  Phospholipid, glycolipid helps in the formation of plasma membrane.Phospholipid contain glycerol head and fatty acid tail.

coal is not sustainable because it will one day run out.

all matter is made up of atoms

in any element all atoms are the same

elements in a compound are always in a constant ratio: apex