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设f(x)是定义在R上单调递减的奇函数,若x1+x2>0,x2+x3>0,x3+...
设f(x)是定义在R上单调递减的奇函数,若x1+x2>0,x2+x3>0,x3+x1>0,则( )
A.f(x1)+f(x2)+f(x3)>0
B.f(x1)+f(x2)+f(x3)<0
C.f(x1)+f(x2)+f(x3)=0
D.f(x1)+f(x2)>f(x3)
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