单项选择题
A.±5mm B.±10mm C.±15mm D.±20mm
A.2% B.3% C.4% D.5%
A.1/75 B.2/75 C.3/75 D.4/75
A.3000MΩ·km B.4000MΩ·km C.5000MΩ·km D.6000MΩ·km
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