单项选择题
A.0.6~0.8mm B.0.5~0.7mm C.0.4~0.6mm D.0.25~0.35mm
A.最大功率 B.牵引力 C.最小功率 D.牵引特性
A.1‰ B.0.5‰ C.2‰ D.1.5‰