If EARTH is coded by replacing each letter with the one three places ahead, the code is

  • A. HDUWK
  • B. BXOQE
  • C. HDUWJ
  • D. FBSUI

Explanation

E becomes H, A becomes D, R becomes U, T becomes W and H becomes K, each three places forward. This particular shift is the Caesar cipher, historically used by Julius Caesar. Working letter by letter and writing the alphabet out in full prevents miscounts.

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