$A$ mass $M$ is suspended from a light spring. An additional mass $m$ added displaces the spring further by a distance $x$. Now the combined mass will oscillate on the spring with period

• A
  $T = 2\pi \sqrt {\left( {\frac{{mg}}{{x\left( {M + m} \right)}}} \right)} $
• B
  $T = 2\pi \sqrt {\left( {\frac{{\left( {M + m} \right)x}}{{mg}}} \right)} $
• C
  $T = \frac{\pi }{2}\sqrt {\left( {\frac{{mg}}{x}} \right)\left( {M + m} \right)} $
• D
  $T = 2\pi \sqrt {\left( {\frac{{\left( {M + m} \right)}}{{mgx}}} \right)} $