Two blocks A and B, having masses m, and m respectively, are placed in contact on a smooth horizontal surface. A force F is applied horizontally on A. The contact force between A and B is

• A.  \[\frac{{{m}_{1}}}{{{m}_{2}}}F\]                              
• B.  \[\frac{{{m}_{2}}}{{{m}_{1}}}F\]
• C.  \[\frac{{{m}_{1}}F}{{{m}_{1}}+{{m}_{2}}}\]        
• D.         \[\frac{{{m}_{2}}F}{{{m}_{1}}+{{m}_{2}}}\]