单项选择题
A.1/6-1/5B.1/5-1/4C.1/4-1/3D.1/3-1/2
A.1/4B.1/2C.3/4D.1/3
A.1.5-2B.0.5-1C.2-2.5D.3-4
A.1B.2C.3D.4
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