ANSWER
A. is created by a current going through a wire
EXPLANATION
A magnetic field can sometimes occur with an electric field. Then, it is called an electromagnetic field.
The lines of a magnetic field never cross and they form loops from north to south.
Also, magnetic fields can be created by the current flowing through a wire.
Hence, of these options, the one that is true is that a magnetic field is created by a current going through a wire.
