The passage is mainly about . A. the structure of the water cycle B. the role of ’Earth’s systems C. the way the planet appears from outer space D. the environment

thinking it would be physical characteristics

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.