Final answer:
Incidence refers to the number of new cases of a disease during a specific time period.
Step-by-step explanation:
Incidence and prevalence are two important measurements of disease occurrence and distribution. Incidence refers to the number of NEW cases of a disease during a specific time period. It is used to understand risk factors and disease spread. Prevalence, on the other hand, refers to the total number of both new and existing cases in a population over time. It provides an indication of the overall health of the population during a time period.
So, the answer to the question is a. Incidence.