Which statement best describes why carbon is the key element in organic compounds? a. carbon is extremely reactive and must form bonds for stability. b. carbon has a strong tendency to form chains or rings. c. carbon is the least reactive element on the periodic table. d. carbon is the most abundant element in the universe.

I believe the answer is B because carbon can easily form chains to bond together.

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.