Answer: Case-control study
Step-by-step explanation:
Case control study can be defined as the type of observational study in which outcomes are identified by observing the changes in controlled and experimental samples. The incidences and frequencies of the rare diseases can be recorded and analyzed using hospital health records this will help in analyzing of the effect and emergence of a particular rare disease in the community or the population located or confined to a particular geographical area. This an example of case control study. Here, in the given study the occurrence of rare diseases and their frequency is compared with normal people in the population.