Which type of nuclear power reactor is used in only 1 percent of all power plants?

Breeder reactors

Explanation:

The type of nuclear power reactor that is used in only 1 percent of all power plants would be Breeder reactors.

answer; i believe the answer is hydraulic action;

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.