<prompt> Which of the following methods is used for demonstrating old washed up blood-stains -Infrared photographyLuminol sprayUltraviolet lightMagnifying lens  <response>: Luminol 3-aminophthalhydrazide spray is most common blood reagent used for visualizingdemonstrating weak faint blood stains i.e old washed up or cleaned up stains and blood stains in areas difficult to see such as outdoor vegetations etc. 