Two wires of the same dimensions but resistivities \[{{\rho }_{1}}\text{ and }{{\rho }_{2}}\] are connected in series. The equivalent resistivity of the combination is [KCET 2003]

• A.         \[{{\rho }_{1}}+{{\rho }_{2}}\]                                  
• B.         \[\frac{{{\rho }_{1}}+{{\rho }_{2}}}{2}\]
• C.         \[\sqrt{{{\rho }_{1}}{{\rho }_{2}}}\]                       
• D.         \[2({{\rho }_{1}}+{{\rho }_{2}})\]