The branch of medical science which is concerned with the study of disease as it affects a community of people is called epidemiology.
The other options are unrelated to this specific area of study:
- Oncology focuses on the study and treatment of cancer.
- Paleontology deals with the study of fossils and prehistoric life.
- Pathology involves the study of diseases, specifically their nature and causes, typically on an individual basis rather than within a community.
In summary, epidemiology is the correct answer as it specifically examines how diseases spread and affect groups of people, aiming to control health problems in the population.