Two spherical bob of masses $M_A$ and $M_B$ are hung vertically from two strings of length $l_A$ and $l_B$ respectively. They are excuting SHM with frequency relation $f_A$ =$2f_B$ , Then :

Question

( A ) $l_A=\frac{l_B}{4}$
( B ) $l_A=\frac{l_B}{2}\&M_A=\frac{M_B}{2}$
( C ) $l_A=2l_B\& M_A=2M_B$
( D ) $l_A=4l_B$