The Very Strong Magnetic Field on a Neutron Star Is

The very strong magnetic field on a neutron star is created by

A) the collapse of the star, which significantly intensifies the original weak magnetic field of the star.
B) differential rotation of the star, with the equator rotating faster than the poles, similar to sunspot formation.
C) a burst of neutrinos produced by the supernova explosion, the equivalent of a very large electrical current flowing for a short time.
D) turbulence in the electrical plasmas during the collapse of the star; the original star would have had no magnetic field.