What Do Sociological Researchers Mean by Unit of Analysis

What do sociological researchers mean by unit of analysis?

A) The unit of analysis is the piece of a topic that a researcher bites off when she or he studies it,whether large or small,local or global.
B) The unit of analysis is a reference to the metric units employed in sociological studies,which sociologists routinely use to conform to the standards of their European colleagues.
C) For sociologists,the unit of analysis is the macro-level object of their studies,whether states,nations,or the world.
D) For sociologists,the unit of analysis is always the individual.