A.1∶0.35~1∶0.50 B.1∶0.50~1∶0.75 C.1∶0.75~1∶1.00 D.1∶1.00~1∶1.25
A.0.5d B.0.85d C.2d D.2.5d
A.L-2c+2×0.268H′ B.L-2c+2×0.414H′ C.L-2c+2×0.577H′ D.L-2c+2×0.115H′