Explanation: While the FCC's Part 97 rules generally do not require amateur radio stations to keep a log for all operations, certain activities, such as handling international third-party traffic, *do* require log entries. Furthermore, many amateurs choose to keep a log for personal records or to document their compliance. When a log is kept, and it contains no entries relating to distress or disaster situations, the standard practice and regulatory guidance for record retention is **two years from the last date of entry**. This period is specified in various parts of FCC regulations for routine station logs across different radio services, and it's commonly applied to amateur logs when they are kept voluntarily or for specific regulated activities. * **C) For a period of two years from the last date of entry** is correct because it aligns with the common FCC standard for routine radio station log retention. * **A) For a period of three years...** is incorrect; the specific duration is two years. * **B) Until authorized by the Commission...** is incorrect for routine logs; this level of authorization is generally reserved for very sensitive or long-term records, not standard operational logs. * **D) Indefinitely, or until destruction is specifically authorized by the U.S. Coast Guard** is incorrect. The retention period is not indefinite, and the U.S. Coast Guard does not authorize the destruction of general amateur radio logs.