Question 31 - GCVR - READINGThe human immunodeficiency virus (HIV) belongs to a certain group of viruses found in many different animals, from horses to humans. Among the viruses in this group, simian immunodeficiency virus (SIV) and feline immunodeficiency virus (FIV) are closest to HIV. By studying these viruses and the relationships between them, researchers hope to be able to explain their progression and gains information that may offer clues about the way viruses like HIV can be overcome. Many biologists believe that SIV evolved in African monkeys and that some time ago there was what is called an adaptive episode. In other words, some of the monkeys were resistant to the virus for genetic reasons and survived the SIV epidemic, while all the others died off, or the virus became less virulent, or some combination of both things happened. either way, there now exists a sort of equilibrium between the host and the virus. Researchers want to study SIV in wild monkeys, but collecting the needed blood samples is problematic, due in part to the endangered species status of the monkeys. They can't be shot with tranquilizer darts, which is necessary to get a blood sample, because that could injure the animals by casing them to fall from tall trees. To solve this problems, the researchers have turned to the lions of the Serengeti plains. Lions infected with FIV offer an almost identical parallel to SIV, except that studying their infection in the wild is far easier than tracking SIV-positive African monkeys. All researchers have to do is sneak up on a lion napping on the ground and shoot it with a tranquilizer dart. the animal will just sleep a little deeper, without suffering any ill effects.   What does the passage suggest about SIV?   It used to be more deadly than FIV.It evolved into HIV.It caused African monkeys to become an endangered species.It was more deadly than it is now.