Paroxysmal Nocturnal Hemoglobinuria is an acquired disease that is the result of a somatic mutation of the phosphotidylinositol glycan protein present on the surface of blood cells.
The gene (and the related disease causing mutation) for this protein is present on the X chromosome !
But in no way should the disease be regarded as an X linked, because it's not at all a genetic disease!
Affected people will not transmit the disease to their offspring because it's a somatic mutation not a germ line mutation.
You either misunderstood the question or the question is a bad non scientific trick.