A wire of length L, area of cross section A is hanging from a fixed support. The length of the wire changes to ${\mathrm{L}}_1$ when mass M is suspended from its free end. The expression for Young’s modulus is 

• A

  $\frac{\mathrm{Mg}({\mathrm{L}}_1-\mathrm{L})}{\mathrm{AL}}$

• B

  $\frac{\mathrm{MgL}}{{\mathrm{AL}}_1}$

• C

  $\frac{\mathrm{MgL}}{\mathrm{A}({\mathrm{L}}_1-\mathrm{L})}$

• D

  $\frac{{\mathrm{MgL}}_1}{\mathrm{AL}}$