The nuclear activity of a radioactive element becomes $\left(\frac{1}{8}\right)^{\text {th }}$ of its initial value in $30\, years.$ The half-life of radioactive element is $....\,years.$

  • [JEE MAIN 2021]
  • A

    $15$

  • B

    $10$

  • C

    $20$

  • D

    $25$

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