单项选择题
A.250m B.300m C.400m D.500m
A.不超过25% B.可大于25%,但不宜超过30% C.25%~30% D.15%~45%
A.1/10000或1/5000 B.1/5000和1/2000 C.1/20000或 1/10000 D.1/2000或 1/1000