Select the option that can be used as a one-word substitute for the given group of words.

The study of population and its dynamics

Demography

The correct option is demography. It means "the statistical study of human populations, especially with reference to size and density, distribution, and vital statistics (births, marriages, deaths, etc.)." The other options are not correct substitutes.

• Democracy is a form of government in which the people hold power.
• Dysgraphia is a learning disorder that affects a person's ability to write.
• Dermatology is the branch of medicine that deals with the skin.