A.1~2 B.2~3 C.1~3 D.3~4
A.2~4倍 B.3~5倍 C.4~7倍 D.6~7倍
A.0.3--0.5m/s B.0.3--0.7m/s C.0.5--1m/s D.0.3--1.5m/s