Sociologists look at collective behavior as the actions of people who are responding to situations.

The socialists tend to understand human behavior in the social context in which it occurs. 
Sociologists look at collective behavior as the actions of ordinary people who are responding to extraordinary situations.

Sociologists look at collective behavior as the actions of ordinary people who are responding to extraordinary situations.

This means that sociology involves the investigation of how "ordinary people" or the masses (rather than just the elite minority, celebrities, politicians, etc.) behave as a whole (collectively) rather than on an individual case-by-case basis.

Furthermore, sociology investigates how the collective or unanimous behavior of the masses (ordinary people) is in response to extraordinary situations (crime, war, corruption, political issues, diseases, etc.) For instance, sociologists might conduct research topics such as how socioeconomic class influences political orientation, and how racism is linked to job success and employment rates. 

Ithink it would be choices a and b. hope this !