The study of population is called demography. Demography is a social science that deals with the statistical study of human populations. It focuses on various aspects such as birth rates, death rates, migration patterns, and population growth or decline.
Option 1, cartography, is the study and practice of making maps. It is not related to studying populations.
Option 2, anthropology, is the study of human societies and cultures. While it may involve studying populations, it is a broader field that encompasses many other aspects of human life.
Option 4, biography, is the study of someone`s life and experiences. It is not specifically related to studying populations.
In conclusion, demography is the correct answer as it specifically refers to the study of population.