When We See X-Rays from an Accretion Disk in a Binary

Multiple Choice

When we see X-rays from an accretion disk in a binary system,we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole.Suppose we then observe each of the following phenomena in this system.Which one would rule out the possibility of a black hole?

A) intense X-ray bursts
B) spectral lines from the companion star that alternately shift to shorter and longer wavelengths
C) visible and ultraviolet light from the companion star
D) bright X-ray emission that varies on a time scale of a few hours