Why Did English Immigration to the American Colonies Decline in the Eighteenth

Why did English immigration to the American colonies decline in the eighteenth century?

A) English authorities stopped encouraging emigration in order to retain skilled laborers and professionals in England.
B) Economic opportunities in the colonies were declining.
C) Disease rates in the colonies had spiked, and many people did not want to risk dying in an epidemic.
D) Economic conditions in England has worsened.
E) Native Americans had regained much of their land, so little land was available to new colonists.