The correct answer is:
The evidence reveals that sugar barons in Cuba and Russia freed enslaved people and serfs.
The authors Marc Aronson and Marina Budhos state that the sugar industry was a fundamental element in leading to the abolition of slavery. While in Russia the beet sugar helped convince nobles to free their serfs, the Cuban planters followed their example convinced that new technology could lead to freedom in Cuba as well.
The authors present this as evidence of sugar having contributed to the liberation of serfs and enslaved people both in Cuba and Russia.