When a pathogen enters the body which blood component helps us attack the pathogen

antibodies

Explanation:

Antibodies have three main functions:

-They neutralize the pathogen,

- Activate other defense cells and  

- Activate the complement system.

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.