This structure is used to radiate protein fibers utilized in proliferation and gametogenesis.

Spindle fiber  

Explanation:  

The centromere is also known as the microtubule organizing center. This structure provides a framework for the means of attachment which keeps the chromosome organized.

It also helps in the alignment and keeps the entire process of mitosis assorted.

It helps in avoiding the incomplete sets of chromosomes and aneuploidy.

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.