Two spherical bob of masses m_A and m_B are hung vertically from two strings of lengths I_A and l_B respectively. They are executing SHM with frequencies f_A and f_B such that ${\mathrm{f}}_{\mathrm{A}}=2{\mathrm{f}}_{\mathrm{B}}$.Then :

• A

  ${\mathrm{l}}_{\mathrm{A}}=\frac{{\mathrm{l}}_{\mathrm{B}}}{4}$

• B

  ${\mathrm{l}}_{\mathrm{A}}=4 {\mathrm{l}}_{\mathrm{B}}$

• C

  ${\mathrm{l}}_{\mathrm{A}}=2{\mathrm{l}}_{\mathrm{B}} \mathrm{and} {\mathrm{m}}_{\mathrm{A}}=2{\mathrm{m}}_{\mathrm{B}}$

• D

  ${\mathrm{l}}_{\mathrm{A}}=\frac{{\mathrm{l}}_{\mathrm{B}}}{2} \mathrm{and} {\mathrm{m}}_{\mathrm{A}}=\frac{{\mathrm{m}}_{\mathrm{B}}}{2}$