A.減小,減小 B.減小,增大 C.增大,減小 D.增大,增大
A.6m/s,4m/s B.6m/s,3m/s C.5m/s,4m/s D.5m/s,3m/s
A.ρν B.ρν/2 C.ρν3 D.ρν3/2