Final answer:
An endemic disease is constantly present in a population, often at a low incidence, such as malaria in tropical regions. Epidemic diseases, like influenza, occur when there is an unusually high number of cases in a short period, and a pandemic disease, like HIV/AIDS, is an epidemic that attains worldwide spread.
Step-by-step explanation:
Distinguishing Between Pandemic, Epidemic, and Endemic Diseases
A disease that is constantly present in a population, often at a low incidence, is referred to as an endemic disease. An example of an endemic disease is malaria in certain tropical regions, where it is transmitted year-round by mosquitoes. In contrast, an epidemic disease occurs when there is an unusually high number of individuals affected in a population at the same time, such as the seasonal spikes in influenza cases. If an epidemic spreads across multiple countries or continents, it may become a pandemic disease, like HIV/AIDS or novel influenza virus outbreaks that attain global spread.
Therefore, the answer to the question is c. endemic, which describes a disease that is constantly present in a population.