An Isolated Black Hole in Empty Intergalactic Space Would Be

An isolated black hole in empty intergalactic space would be difficult to detect because

A) there would be no stars behind it whose light would be affected by gravitational lensing.
B) it could not emit light from inside its event horizon.
C) no companion stars would be affected by its gravitational field.
D) no matter would be falling into it to create an X-ray-emitting accretion disk.
E) All of the other choices are correct.