Black holes emit x-rays lights from within their event horizons (I believe this one is unknown because you cannot see what's going on inside event horizon)
A 9 km black hole may be hidden between Saturn and Jupiter (I think it's true because the distance between these planets are larger than 9km).
A black hole in a binary system will suck in its companion (Not sure about this one because I don't think the effect is large in a non-close binary system)
Singularity of black hole has infinite density (I guess it is true but can't find evidence)
Could someone give any suggestion, please?