Why Is the Material That Accretes onto a Neutron Star

Multiple Choice

Why is the material that accretes onto a neutron star or black hole expected to emit X-rays?

A) The material contains magnetic fields that will produce synchrotron radiation.
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.