There are $10^{10}$ radioactive nuclei in a given radioactive element. Its half-life time is $1 \text{ minute}$. How many nuclei will remain after $30 \text{ seconds}$? $(\sqrt{2} = 1.414)$

  • A
    $2 \times 10^{10}$
  • B
    $7 \times 10^{9}$
  • C
    $10^{5}$
  • D
    $4 \times 10^{10}$

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