单项选择题
A.5°～15° B.15°～30° C.30°～60° D.45°～60°
A.10°～30° B.15°～0° C.30°～60° D.45°～60°
A.10 mm B.20 mm C.40 mm D.50 mm
A.10mm B.30mm C.40mm D.50mm
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