4. What glands are located on the kidneys? What body system are they a part of?

adrenal gland are located on kidneys .

they are a part of glandular system .

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

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.