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21,23,26,31,38,(),62。 A.47B.49C.51 D.53
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3,2,3,7,18,() A.47B.24C.36D.70
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3,6,11,18,(),38。A.23B.25C.27 D.29
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-1,6,7,18,(),38A.18B.21 C.23D.27
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6,7,18,23,38,()A.47B.53C.62D.76
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6,7,18,23,(),47 A.25 B.38 C.40 D.50
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76×(1/23-1-63)+23×(1/53+1/76)-53×(1/23-1/76)=()。A.15/38B.15/76C.1D.2