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1,1,2,6,15,() A.21;B.24;C.31;D.40;
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:1,2,6,15,31,()A.46 B.61 C.66 D.56
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1,2,6,15,31,()。 A.40 B.56 C.36 D.62
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1.2,6,15,31.()。A.46B.61C.66D. 52
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1,2,6,15,31,()A.46 B.61 C.66 D.56
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6, -1, 14, 11, 30, ()。A.31 B.42 C.52 D.56
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2,6,13,39,15,45,23,()。A.46B.66 C.68D.69