Final answer:
The most affected product by the Stamp Act would be a marriage certificate, as the Act specifically taxed legal documents and other printed materials.
Step-by-step explanation:
The product most likely to have been affected by the Stamp Act in British North America would be C) a marriage certificate. The Stamp Act of 1765 required that many printed materials in the colonies carry a tax stamp. This included documents such as newspapers, pamphlets, licenses, and legal papers, which directly impacted a marriage certificate. Compared to the other options, sugar was affected by the Sugar Act, the fur coat and the tea were not direct subjects to the Stamp Act but could have been affected by other trade-related taxes like the Townshend Duties.