The Material That Accretes onto a Neutron Star or Black

The material that accretes onto a neutron star or black hole is expected to emit x-rays because

A) the material will produce synchrotron radiation because of the strong magnetic field.
B) hydrogen nuclei begin to fuse and emit high energy photons.
C) the material will become hot enough that it will radiate most strongly at x-ray wavelengths.
D) as the material slows down it converts thermal energy to gravitational potential energy.
E) none of the above