Instructions: In this task, you are given a question and answer options for that question. Using this information, you have to classify each text into different topics: medicine, nursery, psychology, chemistry, pharmacology, biology.
Input: Question: In a cohort study, the number of new cases of disease per person per unit of time is: 
 Options:  <0> The annual incidence. <1> The cumulative incidence or probability. <2> The prevalence rate <3> The density or incidence rate. <4> The relative risk of developing the disease.
Output:
medicine