单项选择题
A.20mm B.25mm C.30mm D.50mm
A.1.0m B.1.5m C.2.0m D.2.5m
A.1.8m B.2.4m C.3.0m D.3.5m
A.0.7m B.0.8m C.0.9m D.1.0m
A.0.3m B.0.4m C.0.5m D.0.6m
A.1.2m B.1.4m C.1.6m D.1.8m
A.2.5m B.3m C.4m D.4.5m
