A billiard ball moving with a speed of 5 m/s collides with an identical ball originally at rest. If the first ball stops after collision, then the second ball will move forward with a speed of

• A

  $10{\mathrm{ms}}^{-1}$

• B

  $\text{5\hspace{0.17em}}{\mathrm{ms}}^{-1}$

• C

  $\text{2.5\hspace{0.17em}}{\mathrm{ms}}^{-1}$

• D

  $1.0{\mathrm{ms}}^{-1}$