单项选择题
A.0.5m,1m B.0.5m,2m C.1m,0.5m D.1m,2m
A.一 B.二 C.三 D.四
A.L>3000m,F>100m2 B.1000m<L≤3000m,50m2<F<100m2 C.500m<L≤1000m,30mm2<F<50m2 D.L≤500m,F<30mm2