Magnetic Fields in the Milky Way Are Concentrated in the Disk

Magnetic fields in the Milky Way are concentrated in the disk because

A) halo stars are incapable of producing strong magnetic fields.
B) the fields are tied to the charged particles in dense molecular clouds.
C) gravity forces them to sink to the center of the disk.
D) supernovae explosions continually force them toward the middle of the disk.
E) supernovae explosions eliminate magnetic fields from the halo.