Does a bar magnet exert a torque on itself due to its own field '? Does one element of a current-carrying wire exert a force on another element of the same wire ?

Explanation

(d) No force or torque is exerted on any bar magnet due to its own magnetic field.
Similarly no force or torque is exerted on a current element due to magnetic field produced by that element. But if current carrying wire is not straight then on every current element there is some net force or torque due to magnetic fields produced by other current elements of same wire. (For a straight wire, such a force or torque is zero).