[单选题]
A 2.0-kg mass moves with a 4y : so,4trwucy ja*r8y0zx8xspeed of 5.0 m/s. Iw s5 a/vzs y:s0sc:i,ht collides head-on with a 3.0 kg mass at rest. If the collision is perfectly inelastic, 0ss5s h:sz:y v,wcai /what is the speed of the masses after the collision?
A. 10 m/s
B. 2.5 m/s
C. 2.0 m/s
D. 0, since the collision is inelastic