单项选择题
A.30° B.45° C.60° D.75°
A.1/800 B.1/900 C.1/1000 D.1/1200
A.25°～10° B.10°～15° C.1°～5° D.15°～30°
A.25％ B.20％ C.15％ D.5％
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