Which of the following statements is correct? A.
An organ is more complex than a molecule but less complex than a cell
B. An organ is more complex than a cell but less complex than an organism
С.
An organ is more complex than an organ system but less complex than an organism
D
An organ is more complex than an organism but less complex than an organ system

not sure if this is what you'r looking for eubacteria and archaebacteria

ya the other dude is right

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.