Ответ:
a) The United States is the fourth (largest) nation in the world.
b) The U.S. president is one of the (most powerful) men in the world.
c) The queen is the (most prominent) person in Britain.
d) The U.S. is one of the (most prosperous) countries in the world.
e) The Big Sleep was one of the (best) films based on a novel by Chandler.
f) This is one of the (most difficult) crosswords I’ve ever tried.
g) It was one of the (hottest) days of the year.
h) He’s the (strongest) man I ever saw.
i) It was one of the (most frightening) bush fires we ever had.
j) This must be the (worst) hotel in town.
k) It’s the (most reliable) car I ever had.
l)This is the (strangest) film I’ve ever seen.