The amino acids are a combination of

Amino acids are a combination of carbon, hydro- gen, oxygen and nitrogen.

Explanation:

All amino acids have a central carbon atom surrounded by a hydrogen atom.

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.