A mass ‘M' is suspended from a ceiling through a string of length ‘L’. This mass moves in a circle of horizontal radius ‘r’ at constant speed such that it is a conical pendulum. The tension in the string will be

A

$$ \frac {mgL} {(2\sqrt{L^2 - r^2})}$$

B

$$ \frac {mgL} {\sqrt{L^2 }} $$

C

$$ \frac {mgL} {\sqrt{r^2 }} $$

D

$$ \frac {mgL} {(\sqrt{L^2 - r^2})}$$