At 1: 00 a. m., someone breaks a window in the back of a store and robs the safe. on the way out, the thief cuts him or herself on a piece of broken glass. you are a forensic detective called to the scene. you test a sample of blood left behind by the thief. it is o–. while you are there, police bring in a suspect with a cut forearm who was arrested just three blocks from the store. you take a sample of the suspect’s blood and mix it with anti-a. you immediately know that the suspect is not the person who cut himself on the broken glass in the store. how would you know this?