单项选择题
A.5° B.10° C.15° D.20°
A.Ⅰ+Ⅱ+Ⅲ B.Ⅱ+Ⅲ C.Ⅰ+Ⅲ D.Ⅰ+Ⅱ
A.<0.75mm B.0.75~1000mm C.0.75~1000mm D.>1000mm