Far Away from a Black Hole (At the Distance of Another

Far away from a black hole (at the distance of another star) , which of the following is a possible way to detect it?

A) notice what a large amount of star light it blocks from behind it
B) look for the pulsed radio waves it gives off as it rotates like a lighthouse
C) look for the neutrinos that escape from the event horizon
D) search for flickering x-rays being given off from an accretion disk around the black hole, as it "eats" part of a neighbor star
E) you can't fool me, you can never, ever detect a black hole!