(1)c(d+1)even
(2)(c+2)(d+4)even
answer: C
(1)c(d+1)even,说明c even 或者d+1 even 或者 both even
(2))(c+2)(d+4)even说明c+2 even或者d +4even或者 both even
综合,因为d+1和d+4不可能同时 even,因此只有c even.
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