What does comparing dna of different organisms allow us to determine

Comparison of whole genome sequences provides a highly detailed view of how organisms are related to each other at the genetic level. By comparing the sequences of genomes of different organisms, researchers can understand what, at the molecular level, distinguishes different life forms from each other.

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.