[单选题]
00.05: A cart with mass 2m has a velocity v befog712czhw g gz3pn rt;8re it srxuza.tmn8.1xib i+ -7khp(iz d(+xztrikes another cart of mass +nxhizb7 1.zr+d k(uxiax pt.izm(8-3m at rest. The two carts couple and move off together with a velocity
A. $v /5$
B. $2v /5 $
C. $3 v/5 $
D. $ 2 v/3 $
E. $\sqrt{0.4}v$
