Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 31 to 35. Sometimes mail arrives at the post office, and it is impossible to deliver the mail. Perhaps thereis an inadequate or illegible address and no return address. The post office cannot just throw thismail away, so this becomes "dead mail." This "dead mail" is sent to one of the U.S. Postal Service'sdead mail offices in Atlanta, New York, ...

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 31 to 35.

Sometimes mail arrives at the post office, and it is impossible to deliver the mail. Perhaps thereis an inadequate or illegible address and no return address. The post office cannot just throw thismail away, so this becomes "dead mail." This "dead mail" is sent to one of the U.S. Postal Service'sdead mail offices in Atlanta, New York, Philadelphia, St. Paul, or San Francisco. Seventy-five millionpieces of mail can end up in the dead mail office in one year. The staff of the dead mail offices have a variety of ways to deal with all of these pieces of deadmail. First of all, they look for clues that can help them deliver the mail; they open packages in thehope that something inside will show where the package came from or is going to. Dead mail will alsobe listed on a computer so that people can call in and check to see if a missing item is there. However, all of this mail cannot simply be stored forever; there is just too much of it. When a lotof dead mail has piled up, the dead mail offices hold public auctions. Every three months, the publicis invited in and bins containing items found in dead mail packages are sold to the highest bidder

The word “they” in paragraph 2 refers to______.