The rate law for a reaction between the substances A and B is given by rate \[=k{{[A]}^{n}}{{[B]}^{m}}\] On doubling the concentration of A and halving the concentration of B, the ratio of the new rate to the earlier rate of the reaction will be as

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