The magnetic field lines, produced around a straight current-carrying conductor, are concentric circles. Their centres lie on the wire.
So, the correct option is (D): The field consists of concentric circles centred on the wire
The magnetic field is a field created by moving electric charges. It is a force field that exerts a force on materials such as iron when they are placed in its vicinity. Magnetic fields do not require a medium to propagate; they can even propagate in a vacuum. Magnetic field also referred to as a vector field, describes the magnetic influence on moving electric charges, magnetic materials, and electric currents.