答案:
21-25. DBACC 26-30. DBABD 31. CDAAA 36-40. CCADA
41-45. BCACB 46-50. BBDCB 51-55. BBBAB 56-60. BBBCA
61-65. BDCDA 66-70. BCDBB 71-75. CDBBD 76-80. ACBBD
81-85. ACACC 86-90. BAACC