An area of cross-section of rubber string is  2 cm². Its length is doubled when stretched with a linear force of $2\times {10}^5$ dynes. The Young's modulus of the rubber in  $\mathrm{dyne}/{\mathrm{cm}}^2$ will be

• A

  $4\times {10}^5$

• B

  $1\times {10}^5$

• C

  $2\times {10}^5$

• D

  $1\times {10}^4$