答：D
譯：他在1992年末之前就參軍了。自那以來他壹直在軍隊。
析：本題考查完成時態。by the end of +過去時間，壹般用過去完成時，表示在過去某個時間之前就已經完成了的動作。如：We had learned about 3,000 English words by the end of last year.
since then 自從那以來，壹直到現在為止，主句用現在完成時的延續性用法。所以妳的選擇是正確的。
妳說參考答案是B，很有可能是答案給錯了。題目打錯、答案錯誤是有可能的。我在網上找到兩處有這題的。選項還有重復呢，答案也是錯的：
1.九年級英語The Picture of Peace測試題 36~40 CCBCA
37. He _____ the Army by the end of 1992. He ____ in the army since then.
A. joined…is B. has joined…has been
C. had joined…is D. has joined… has been
2. 中考英語動詞時態基礎單選過關100題.附答案(3)
3. 初中英語動詞時態基礎練習(二)、2010年中考英語動詞時態基礎練習100題(8)
86—90 DDBCA
（ ）87. He _____ the Army by the end of 1992. He ____ in the army since then.
A. joined…is B. has joined…has been C. had joined…is D. has joined… has been
選項B和D竟然是壹樣的。
妳的題還算不錯，將D項改回來了，改正確了。