Answer: A. Diseases will increase.
Step-by-step explanation:
A limiting factor is the one which is potent enough to limit the growth, abundance and distribution of the population of species in an ecosystem. Carrying capacity is the maximum number of the population of species which an ecosystem can support by availing resources. If the population exceeds above the carrying capacity, it starts declining.
According to the situation given, diseases will increase is the correct option. Diseases can be limiting factor for reducing the population of humans in an area. Hence, will maintain the carrying capacity.