Answer: A. the one-drop rule depended on a nonexistent ability or test to detect, biologically, the presence of racial impurities.
Step-by-step explanation:
The one-drop rule is a system of classifying an individual to a particular race just because one of his/her ancestor is of Sub-saharan origin despite the physical appearance (phenotype) of the individual. The short coming of this rule is that there is no scientific test carried out to determine the individuals genetic make up.