What commercial settlement with Spain gave Britain a monopoly over the slave trade at the end War of the Spanish Succession (Queen Anne’s War?)

Question

The Treaty of Utrecht which ended Queen Anne’s war in 1712 gave Britain a decisive monopoly over the Slave Trade in the Western Hemisphere. Britain had already dominated the slave trade since it had rested commercial concessions from Spain foremost of which was El Pacto del Asiento de Negros known as the Asiento (1713). This commercial agreement gave Britain’s South Sea Corporation exclusive rights to supplying Spanish America with slaves until 1742. The Asiento not only guaranteed a monopoly over the slave trade but also served to mask Britain’s attendant goal of selling goods and establishing a thriving underground slave market in the Caribbean and throughout Latin America. 

Answer 1

El Pacto del Asiento de Negros known as the Asiento (1713) is the correct answer. The next sentence after it is mentioned tells you it was a commercial agreement. Two sentences later it says, "The Asiento...guaranteed a monopoly over the slave trade...".