Social demography is the study of:

Population

The correct answer is Option (2) - Population

Social demography focuses on the quantitative study of populations, including their composition, distribution, trends, and characteristics. It involves analyzing various demographic variables such as age, gender, race, ethnicity, marital status, fertility, mortality, migration, and socioeconomic status within populations.

Population studies or social demography, on the other hand, enquires into the wider causes and consequences of population structures and change. Social demographers believe that social processes and structures regulate demographic processes; like sociologists, they seek to trace the social reasons that account for population trends