A.6 | B.7 | C.8 | D.9 |
n(n-1)(n-2)(n-3) |
4×3×2×1 |
A.60种 | B.48种 | C.36种 | D.24种 |
A.C302C202C461 |
B.C505-C305-C205 |
C.C505-C301C204-C304C201 |
D.C303C202+C302C203 |
A.Cm1Cn2+Cn1Cm2 | B.Cm1Cn2+Cn-11Cm2 |
C.Cm-11Cn2+Cn1Cm2 | D.Cm-11Cn2+Cn-11Cm-12 |
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