单项选择题
A.<55mm,<1% B.<50mm,<1.5% C.<50mm,<1% D.<60mm,<1%
A.2倍;0.3m B.1.5倍;0.6m C.2倍;0.9m D.2倍:1m
A.2m B.2.5m C.3m D.3.5m