One end of a long metallic wire of length L is tied to the ceiling. The other end is tied to a massless spring of spring constant k. A mass m hangs freely from the free end of the spring. The area of cross-section and the Young's modulus of the wire arc A and Y respectively. If the mass is slightly pulled down and released, it will oscillate with a time period T equal to:
 

• A

  $2\mathrm{\pi }\sqrt{\left(\frac{\mathrm{m}}{\mathrm{k}}\right)}$

• B

  $2\mathrm{\pi }\sqrt{\frac{\mathrm{m}\left(\mathrm{YA}+\mathrm{kL}\right)}{\mathrm{YAk}}}$

• C

  $2\mathrm{\pi }\sqrt{\left(\frac{\mathrm{mYA}}{\mathrm{kL}}\right)}$

• D

  $2\mathrm{\pi }\sqrt{\frac{\mathrm{mL}}{\mathrm{AY}}}$