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

a)
Native Americans had regained much of their land, so little land was available
to new colonists,

b)
Disease rates in the colonies had spiked, and many people did not want to
risk dying in an epidemic.

C)English authorities stopped encouraging emigration in order to retain skilled
laborers and professionals in England.

d) Economic conditions in England has worsened.
e) Economic opportunities in the colonies were declining.

e) Economic opportunities in the colonies were declining