Two bodies with masses \[{{m}_{1}}\] and \[{{m}_{2}}\] \[({{m}_{1}}>{{m}_{2}})\] are joined by a string passing over a fixed pulley. The centres of gravity of the two bodies are initially at the same height. Assume mass of the pulley and weight of the thread negligible. Then the downwards acceleration of \[{{m}_{1}}\] is

• A.  \[\left( \frac{{{m}_{1}}-{{m}_{2}}}{{{m}_{1}}+{{m}_{2}}} \right)g\]            
• B.  \[{{\left( \frac{{{m}_{1}}-{{m}_{2}}}{{{m}_{1}}+{{m}_{2}}} \right)}^{2}}g\]
• C.  \[\frac{{{m}_{2}}g}{{{m}_{1}}+{{m}_{2}}}\]        
• D.         \[\frac{{{m}_{1}}g}{{{m}_{1}}+{{m}_{2}}}\]