单项选择题
A.450.0 B.500.0 C.550.0 D.600.0
A.5000.0 B.5500.0 C.5050.0 D.5800.0
A.0.5 B.0.6 C.0.7 D.0.8
A.1.0 B.2.0 C.3.0 D.4.0
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