The only factorial expression that is shown properly evaluated is that of selection A.
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If you number the terms starting from 0 on the left, you find that 20 is term #3 on the row that has 6 as term #1. In combination notation, this would be
... 6C3 or C(6, 3)
It is computed as
... 6!/(3!·(6-3)!) = 6·5·4/(3·2·1) = 20
