单项选择题
A.±2.0% B.±2.5% C.±5% D.±10%
A.25~30 B.20~25 C.15~20 D.10~15
A.0.5% B.1% C.1.5% D.2%
A.1:1 B.2:1 C.3:1 D.4:1
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