A. Observing the activity.B. Evaluating the activity.C. Monitoring the activity.D. Controlling the activity.请阅读Passage l。完成第21—25小题。Passage 1It's one of our common beliefs that mice are afraid of cats. Scientists have long known that even if a mouse has never seen a cat before, it is still able to detect chemical signals released from it and run away in fear. This has always been thought to be something that is hard-wired into a mouse s brain.But now Wendy Ingram, a graduate student at the University of California, Berkeley, has challenged this common sense. She has found a way to""cure"" mice of their inborn fear of cats by infecting them with a parasite, reported the science journal Nature.The parasite, called Toxoplasma gondii, might sound unfamiliar to you, but the shocking fact is that up to one-third of people around the world are infected by it. This parasite can cause different diseases among humans, especially pregnant women--it is linked to blindness and the death of unborn babies.However, the parasite's effects on mice are unique. Ingram and her team measured how mice reacted to a cat's urine(尿) before and after it was infected by the parasite. They noted that normal mice stayed far away from the urine while mice that were infected with the parasite walked freely around the test are