'Death rate' of a country can be understood as a :

Social phenomenon

The correct answer is Option (2) → Social phenomenon

Demographic data are important for the planning and implementation of state policies, specially those for economic development and general public welfare. But when they first emerged, social statistics also provided a strong justification for the new discipline of sociology. Aggregate statistics – or the numerical characteristics that refer to a large collectivity consisting of millions of people – offer a concrete and strong argument for the existence of social phenomena. Even though country-level or state-level statistics like the number of deaths per 1,000 population – or the death rate – are made up by aggregating (or adding up) individual deaths, the death rate itself is a social phenomenon and must be explained at the social level.