Answer:
The correct option is "moving electric charges or currents".
Explanation:
Magnetic field is used to define as a field that surrounds a current carrying conductor or moving electric charge by virtue of which it exerts a force on another current carrying conductor or a moving charge itself.
The magnetic field generated by a moving charge is given by
where
q = is the magnitude of charge
v = is the velocity vector of the moving charge
r = is the position vector of the point at which the field is calculated
|r| = is the magnitude of position vector.
Similar the magnetic field generated by a current carrying conductor is given by
where
I is the current
The integration is carried out along the whole length of conductor.
Also since magnetic mono poles do not exist or their existence is not confirmed until now so it is not an appropriate option.