A goods train accelerating uniformly on a straight railway track, approaches an electric pole standing on the side of track. Its engine passes the pole with velocity u and the guard's room passes with velocity v. The middle wagon of the train passes the pole with a velocity.

• A. \[\frac{\text{u+v}}{2}\]
• B. \[\frac{1}{2}\sqrt{{{\text{u}}^{\text{2}}}\text{+}{{\text{v}}^{\text{2}}}}\]
• C. \[\sqrt{\text{uv}}\]                                
• D. \[\sqrt{\left( \frac{{{\text{u}}^{2}}+{{\text{v}}^{2}}}{2} \right)}\]