Why do scientists hypothesize that chemical reactions and molecular activity preceded life on earth?

The chemicals of life must have preceded the formation of life on earth. This is especially true in the formation of organic molecules especially DNA and RNA and amino acids. Spontaneous reactions in the oceans from chemicals from methane, water, hydrogen, ammonia, and etcetera, occurred in the waters. Energy from the sun and lightning strikes spurred these spontaneous reactions. These organic compounds in the waters when aggregated underwent formations to form photobionts, the precursors of life.

Answer : romans built laws to manage the pollution which was lead by smoke produced by the factories.

they had the law tat factories that produces smoke cannot be built near residential buildings.

building of proper sewage system was done to ensure that the waste is carried away from the humans so that they do not get diseases from it.

also they built water systems to provide water in those areas which are drought prone.