Q.
A and B are fixed points and the mass M is tied by strings at A and B. If the mass M is displaced slightly out of this plane and released, it will execute oscillations with period ( given $AM = BM = L,AB = 2d$)
A) $2\sqrt{\frac{L}{g}}\pi$
B) $2\pi\sqrt{\frac{\left( L^{2} - d^{2} \right)^{1/2}}{g}}$
C) $2\pi\sqrt{\frac{\left( L^{2} + d^{2} \right)^{1/2}}{g}}$