Final answer:
The most powerful weapon the plantation masters had was the threat of sale. By instilling fear, they controlled the actions of the enslaved people.
Step-by-step explanation:
The most powerful weapon the plantation masters had was the threat of sale. By threatening to sell slaves, the masters instilled fear and controlled the actions of the enslaved people. This fear of being separated from family and friends created a constant state of terror and ensured compliance with the masters' wishes.