单项选择题
A.180° B.120° C.90° D.60°
A.0.10~0.20 B.0.25~0.35 C.0.40~0.60 D.0.65~0.75
A.0.15~0.25 B.0.30~0.40 C.0.45~0.65 D.0.70~0.80