单项选择题
A.1 B.1.5 C.2.0 D.3.0
A.丈量1000m,误差±50mm B.丈量100m,误差±20mm C.丈量10m,误差±10mm D.丈量lm,误差±lmm
A.5m B.10m C.15m D.20m