共35种,分别是:abcd abce abcf abcg abde abdf
abdg abef abeg abfg
bcde bcdf bcdg bcef bceg bcfg
bdef bdeg bdfg befg
cdef cdeg cdfg cefg
defg
共35种,分别是:abcd abce abcf abcg abde abdf
abdg abef abeg abfg
bcde bcdf bcdg bcef bceg bcfg
bdef bdeg bdfg befg
cdef cdeg cdfg cefg
defg