根据以下材料，回答
It′s one of our common beliefs that miceare afraid of cats. Scientists have long known that even if a mouse has neverseen a cat before, it is still able to detect chemical signals released from itand run away in fear. This has always been thought to be something that is hard-wiredinto a mouse′ s brain.
But now Wendy Ingram, a graduate student atthe University of California, Berkeley, has challenged this common sense. Shehas found a way to "cure" mice of their inborn fear of cats by infectingthem 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 ofpeople around the world are infected by it. This parasite can cause different diseasesamong humans, especially pregnant women--it is linked to blindness and thedeath of unborn babies.
However, the parasite′s effects on mice areunique, 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 thatnormal mice stayed far away from the urine while mice that were infected withthe parasite walked freely around the test area.
But that′s not all. The parasite was foundto be more powerful than originally thought--even after researchers cured themice of the infection. They no longer reacted with fear to a cat′s smell, whichcould indicate that the infection has caused a permanent change in mice′ sbrains.
Why does a parasite change a mouse′s braininstead of making it sick like it does to humans? The answer lies in evolution.
"It′s exciting scary to know how aparasite can manipulate a mouse′s brain this way," Ingram said. But shealso finds it inspiring. "Typically if you have a bacterial infection, you go to a doctor andtake antibiotics and the infection is cleared and you expect all the symptomsto also go away." She said, but this study has proven that wrong. "This may have huge implicationsfo
A.positive
B.subjective
C.negative
D.objective