【正确答案】 Most scientists believe that crude oil is formed by the decomposed remains of countless billions of tiny plants and animals which lived in the sea tens of trillions of years ago. Once these creatures died, their bodies would decompose, and then formed slime layers in the deep sea millions of years later. With common reaction of the extrusion of the crustal movement and the resulting heat, these slime layers would become oil.
Petroleum distillates (which form the mixture of oil) and its byproducts are innumerable, which include: gasoline for cars, diesel for trains, buses, cargo trucks, lubricating oil for all kinds of engines , heavy fuel for power stations and ships, pitch for pacing, and petrochemicals for manufacturing plastics, synthetic fibre, or even fabricated food, etc. At present, it is hard to imagine a world without oil products.