Dr. John Snow found that cholera cases in London were

randomly distributed across London.
transmitted through the air in contagious diffusion.
spatially associated with certain public water pumps.
being punished for their sins. spread through trade routes by infected rats.

Spatially associated with certain public water pumps.

Explanation:

Dr. John Snow was a Physician and regarded as the father of epidemiology.

During the cholera outbreak in the 1800s which killed thousands of people in the United Kingdom , he traced the source of the outbreak.

Before then cholera was believed to be an airborne disease but he refuted this and helped in discovering that the source of the outbreak was as a result of certain public pumps. He then urged the council to disable the pumps and this helped in solving the cholera outbreak problem.

Dr. John Snow found that cholera cases in London were "spatially associated with certain public water  pumps".

Explanation:

Cholera is a disease suffered from bad drinking water which the Doctor discovered that some major water pumps in London have due to the volume of impact  of cholera in the environment receiving such supplies of water.

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