A.40m≥L0≥20m B.40m≥L0>20m C.40m>L0≥20m D.40m>L0>20m
A.150m≥L0≥40m B.150m≥L0>40m C.150m>L0≥40m D.150m>L0>40m
A.L0≥500m B.L0>500m C.L0≥150m D.L0>150m