[单选题]
00.05: A cart with mass 2m has a velofv- d*- gwscc;city v before it strikes another cart of m54j;0bm zgl ubh/i(jc ass 3m at rest. The two carts coupliz4(mlbhug/;jc0j 5b e and move off together with a velocity
A. $v /5$
B. $2v /5 $
C. $3 v/5 $
D. $ 2 v/3 $
E. $\sqrt{0.4}v$
