The establishment of in virginia resulted in the importation of indentured servants and african slaves to that colony.

The establishment of "Tobacco as a major Cash Crop" is the right answer.

John Rolfe introduced Tobacco (a commercial crop) in the colony of Virginia in 1612. During the course of time, Tobacco became the basis of the Economy of Colonial Virginia. The cultivation of tobacco required a big labor force, hence, the colonists used to purchase the bound servants and slaves to cultivate it.

american troops were forced to withdraw following deadly bombings.

explanation:

porter is writing economic history because he is focusing on the cost of developing vaccines.