B. <span>a shield of missiles over the U.S. designed to shoot down incoming nuclear missiles from the USSR</span>
Answer:
Because of the great economic gains
Explanation:
The Southern economy relied heavily on agriculture and proceeds brought from it and so the slaves were important as they worked on the farms to produce food and other materials that could be used or exported.
This reliance on slaves and the reluctance to let them go was also increased with the invention of cotton gin.
Abolitionists take action
