[单选题]
00.05: A cart with mass 2m has a velocity v before it strikes anoth(tpous) hlsl9 gw216mgl(a(eer cart of lxnr ck9:opj0 z.( yg.mass 3m at rest. The two carts couple a(cn.l r o9gyjkxp:.0znd move off together with a velocity
A. $v /5$
B. $2v /5 $
C. $3 v/5 $
D. $ 2 v/3 $
E. $\sqrt{0.4}v$