A person travels along a straight road for the first I half length with a velocity \[{{u}_{1}}\] and the second half length with a velocity \[{{u}_{2}}\]. Then the mean velocity y is given by

• A. \[u=\frac{{{u}_{1}}+{{u}_{2}}}{2}\]
• B. \[u=\sqrt{{{u}_{1}}{{u}_{2}}}\]
• C. \[u=\sqrt{\frac{{{u}_{1}}}{{{u}_{2}}}}\]
• D. \[\frac{2}{u}=\frac{1}{{{u}_{1}}}+\frac{1}{{{u}_{2}}}\]