Correct Answer - A
The torque acting on the coil
`|vec(tau)|=|vecm xx vec B|=mB sin theta`
Here the circular coil is placed normal to the direction of magnetic field then the angle between the direction of magnetic moment `(vecm)` and magnetic field `(vecB)` is zero. then
`tau=m B sin theta= m B sin 0=0" "therefore" "tau=0`