Two exactly similar wires of steel and copper are stretched by equal forces. If the difference in their elongations is 0.5 cm, the elongation (I) of each wire is

$\begin{array}{l}{\mathrm{Y}}_{\mathrm{s}}\left(\text{ steel }\right)=2.0\times {10}^{11}\mathrm{N}/{\mathrm{m}}^2\\ {\mathrm{Y}}_{\mathrm{c}}\left(\text{ copper }\right)=1.2\times {10}^{11}\mathrm{N}/{\mathrm{m}}^2\end{array}$

• A

  ${\mathrm{l}}_{\mathrm{s}}=0.75\mathrm{cm},{\mathrm{l}}_{\mathrm{c}}=1.25\mathrm{cm}$

• B

  ${\mathrm{l}}_{\mathrm{s}}=1.25\mathrm{cm},{\mathrm{l}}_{\mathrm{c}}=0.75\mathrm{cm}$

• C

  ${\mathrm{l}}_{\mathrm{s}}=0.25\mathrm{cm},{\mathrm{l}}_{\mathrm{c}}=0.75\mathrm{cm}$

• D

  ${\mathrm{l}}_{\mathrm{s}}=0.75\mathrm{cm},{\mathrm{l}}_{\mathrm{c}}=0.25\mathrm{cm}$