Answer:
The fact that Barack Obama is largely perceived as a black man is illustrative of Option B : The one drop rule.
Explanation:
The one-drop rule originates from laws that were passed in some states like Tennessee and Virginia in the early 20th century. These laws held that any person with some degree of sub-Saharan African ancestry (for example, having "one drop" of black blood) is considered to be African American or black. It is also an example of what is called hypodescent. This means that children of mixed ancestry or race, in this case, are automatically assigned to the social category with lower status.