Five cells each of emf E and internal resistance r send the same amount of current through an external resistance R whether the cells are connected in parallel or in series. Then the ratio \[\left( \frac{R}{r} \right)\] is

• A. \[2\]
• B. \[\frac{1}{2}\]
• C. \[\frac{1}{5}\]
• D. \[1\]