单项选择题
A.0.5 B.0.4 C.0.3 D.0.2
A.0.2 B.0.15 C.0.3 D.0.4
A.2 B.1.5 C.1.8 D.2.5
A.±1.5 B.±2.0 C.±2.5 D.±1.0
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