Wild elephants can tell whether a voice comes from a man,woman or boy,a new study says.That's what researchers found when they played recordings of people for elephants in Kenya.Scientists say this is an advanced thinking skill that other animals haven't shown.It lets elephants figure out who is a threat and who isn't.The result shows that the clever animals are also studying people,said study author Karen McComb. "Basically they have developed this very rich knowledge of the humans that they share their habitat with,"said McComb,a professor at the University of Sussex in England."Memory is key.They must build up that knowledge somehow." The study was released on Monday in the Proceedings of the National Academy of Sciences. It's close but not quite like the Dr.Seuss book,where the elephant Horton hears something that others can't hear. McComb and colleagues went to Amboseli National Park in Kenya,where hundreds of wild elephants live among humans,sometimes coming in conflict over scarce water.The scientists used voice recordings of Maasai men,who on occasion kill elephants,and Kamba men,who are less of a threat to the elephants. As a result,the elephants reacted defensively﹣retreating and gathering in a bunch﹣more to the Maasai language recording because it was associated with the more threatening human tribe,said study co﹣author Graeme Shannon. They repealed the experiment with recordings of Maasai men and women.Since women almost never spear elephants,the animals reacted less to the women's voices.The same thing happened when they substituted young boys'voices."Making this kind of time distinctions in human voice patterns is quite remarkable,"said Emory University animal cognition expert Frans de Waal,who was not part of the study. 24.Who were the people taking part in the study?　 　 A.Frans de Waal and Karen McComb. B.Graeme Shannon and Frans de Waal. C.Dr.Seuss and Graeme Shannon. D.Karen McComb and Graeme Shannon. 25.What can wild elephants benefit from their special ability?　 　 A.Identifying and avoiding possible danger. B.Crowing much faster than any other animals. C.Having a better understanding of humans. D.Developing their language skills. 26.Which can replace the underlined word"substituted"in the last paragraph?　 　 A.distinguish B.repeat C.use D.compare 27.What does the passage mainly talk about?　 　. A.Wild elephants can distinguish between human languages. B.The conflict between humans and wild elephants is growing. C.Wild elephants use language skills to make discrimination. D.Wild elephants can build up good memory and learn tricks.