A force of 6.4 N stretches a vertical spring by 0.1 m. The mass that must be suspended from the spring so that it oscillates with a period of ($\mathrm{\pi }/4$) sec is:

• A

  $\left(\mathrm{\pi }/4\right)\mathrm{kg}$

• B

  1 kg

• C

  $\left(1/\mathrm{\pi }\right) \mathrm{kg}$

• D

  10 kg