单项选择题
A.5+1B.4.5+1C.4.5±1D.5±1
A.20-40B.20-50C.0-20D.5-30
A.90.5±0.5B.115.5±1C.90.5±1D.115.5±0.5
A.1/1000B.2/1000C.3/1000D.4/1000
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