[单选题]
00.05: A cart with mass 2m has a velocity v before it mnqzh+as 8p by*848anstrikes another d+km/.sv le2+m ;iibncart of mass 3m at rest. The two carts couple and move off tne sd klvmii+2m.+ ;b/ogether with a velocity
A. $v /5$
B. $2v /5 $
C. $3 v/5 $
D. $ 2 v/3 $
E. $\sqrt{0.4}v$
