What was the main reason for the pro-slavery attitude of French merchants and plantation owners?

Correct answer: Their economic profit depended on slave labour and trade

The governing concept is the relationship between slavery and colonial economic profit. French merchants earned from overseas commerce, while plantation owners depended on a labour system that produced valuable commodities such as sugar and coffee at low monetary cost to the owners. Ending slavery threatened property claims, labour control and the profits connected with colonial trade. Option B is correct because it identifies the material interest behind the pro-slavery attitude. Option A states the opposite of their position. Option C confuses commercial groups with revolutionary military personnel, and option D places them among the prisoners associated with the Bastille. The question asks for the principal cause, so economic dependence is more precise than a vague reference to politics.