c) The diseases in city A can be controlled by eliminating the reasons for their spread. So we can take the following steps to eliminate the disease-causing reasons:
i. Proper drainage system
With a proper drainage system flow of wastewater is maintained. Thus water does not stagnate and it can help in preventing various water-related diseases. For example, mosquito breeding will be reduced, and thus diseases like dengue fever, chikungunya can be controlled.
ii. Availability of clean and safe drinking water
Clean drinking water will prevent the spread of water-borne diseases such as cholera.
iii. Waste disposal systems
To ensure cleaner surroundings waste must be disposed off properly. Waste must be dumped in sanitary landfills away from the city. Wastewater must be treated first before dumping into rivers.