A clock has a long pendulum made of brass. Due to a temperature change of $20°\mathrm{C}$ the time period of oscillation of the pendulum is found to change by 0.02 %.  The coefficient of linear expansion of brass is

• A

  $2\times {{10}^{-}}^5/°\mathrm{C}$

• B

  $4\times {{10}^{-}}^5/°\mathrm{C}$

• C

  $1\times {{10}^{-}}^5/°\mathrm{C}$

• D

  $0.5\times {{10}^{-}}^5/°\mathrm{C}$