A Red Giant Star Is Found to Be Orbiting an Unseen

A red giant star is found to be orbiting an unseen object with a short orbital period. By measuring the speed at which it orbits, astronomers deduce that the object has a mass of 10M _$\odot$ This object is probably a __________ because __________.

A) black hole; the giant star is massive and could only be in orbit about something even more massive
B) black hole; its mass is too large to be a neutron star or a white dwarf
C) neutron star; any supernova that would have made a black hole would have destroyed the red giant
D) M-dwarf star; only such stars would be faint enough to go unseen in this system
E) black hole; most red giants orbit neutron stars, and neutron stars can turn into black holes