Question

Though no longer a series of colonies, the United States retains close ties to Britain as
a. a commonwealth
b. a dependency
c. a dominion
d. part of a “special relationship

Answer 1

Though no longer a series of colonies, the United States retains close ties to Britain as "d. part of a “special relationship”" since trade between these two nations benefits both immensely.
Answer from "HistoryGuy" on another user's same question.  Not from me.

Answer 2

Though no longer a series of colonies, the United States retains close ties to Britain as part of a “special relationship
So the answer is d.