单项选择题
A.5~15min B.15~30min C.30~45min D.45~60min
A.0.1~0.5取0,0.6~0.9取1.0 B.0.1~0.5取0.5,0.6~0.9取1.0 C.0.1~0.5取0,0.6~0.9取0.5 D.0.1~0.5取0.5,0.6~0.9取0.5
A.真航线 B.推算航线 C.恒向航线 D.计划航线