NO.  Students listening to an instructor constitute a "classroom" but not a social class!

Both A & B are correct answers:

Sociologists often use the term "class" to refer to the paid labor force and the different values and status they are perceived to have. One's class status is also directly related to one's access to social and economic resources. The upper class has the greatest access to economic resources and political power, while the lower and middle classes have proportionately less access.