The correct answer to this question is B) Both were denied political rights because of their race.
The similarity between affranchis and African slaves in Saint-Domingue before the Haitian Revolution is that both were denied political rights because of their race.
Affranchi is a French legal term to identify emancipated slaves, but the term was used to name mulattoes in a pejoratively way. The people considered affranchis had some legal and social advantages in comparison to the slaves from Africa. Affranchis could own land, study in school, and were accepted in some French social activities
However, the affranchies could not vote, work in professions such as doctor or lawyers, and in any colonial administrative posts.
The other options of the question were A) Both were frequently forced to fight in Napoleon armies, C) Both were forced to work in plantations owned by French aristocrats, and D) Both were required to give most of their earnings to the French government.