At two stages of disintegration, disintegration constants are respectively $1\times {10}^{-2}{\mathrm{s}}^{-1}\text{ and }1\times {10}^{-5}{\mathrm{s}}^{-1}$. At first stage 2000 atoms are disintegrating. At second stage number of atoms disintegrating would be

• A

  2

• B

  $2\times {10}^6$

• C

  $2\times {10}^{-6}$

• D

  $2\times {10}^9$