Two radioactive substances A and B have decay constants \[5\lambda \] and \[\lambda \] respectively. At t=0 they have the same number of nuclei. The ratio of number of nuclei of A to those of B will be \[{{(1/e)}^{2}}\] after a time interval

• A. \[4\lambda \]
• B. \[2\lambda \]
• C. \[1/2\lambda \]
• D. \[1/4\lambda \]