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 [AIEEE 2003]

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