单项选择题
A.2/3 B.1 C.2 D.3
A.x+y+z+2=0 B.x+y-z+2=0 C.x-y+z+2=0 D.x+y+z-2=0
A.-x+y+z-4=0 B.x-y-z-4=0 C.x+y+z=0 D.x+y-z+2=0
A. B. C. D.
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