Ants have a reputation for strength,organization and teamwork.But researchers have now discovered that a key secret to the success of ants is their ability to identify the importance of age in the work place. A study of Gentral American leaf-cutter ants has shown that the younger and stronger members are give the toughest job of cutting therough the leaves they harvest.Their sharp youn teeth do this job effectively,but as they get older their teeth become relatively worn and blunt. But rather than being retired or abandoned by the group,the ageing ants are given a new role more suyted to their physical abilities.They become carriers and teansport the leaves back to the kingdom where they are harvested for food. The findings by researchers from the University of Oregon and the Oregong State University support previous research showin the survival of a leaf-cutter kingdom depends on the efficiency(效率）of is workers. “Cuting leaves is hard work,”said Dr.Robert Schofield,who led the research team.“Much of the cutting is done with a V-shaped blade(刀片）between teeth on their jaws.This blade starts out as sharp as the sharpest razor blade that humans have developed.”But over rime the teeth become blunter and the cutting job slows down.The team estimated that,because of this age-related wear,a colony(蚁群)spent twice the energy cutting leaves than it would if all the ants had sharp blades.Its findings support the idea that wear and break can be significant problems for insects as well as largre animals. Like humans,leaf-cuttre ant recognize that older members of the group can still make a worhwhile contribution to society.“This study shows an advantage of social living that we are familiar with,”said Dr.Schofield. 小题1:The younger and stronger ants do the toughest job because . A．they can teansport the leaves effectively B．they have a sharp blade to cut leaves C．other members are busy with other work D．they can finish the job in a better organized way 小题2:The undrelined word“blunt”in the second paragraph can be replaced by . A．quite loose B．less sharp C．quite fragile D．more dirty 小题3:What happens to the ants when they become old? A．They no longer hve work to do. B．They keep doing the same work. C．They have to leave and live on themselves. D．They are given a new worthwhile job. 小题4:It can be learned from the passage that . A．Dr.Schofield is the first to research leaf-cuttre ants B．older ants are more powerful in carrying leaves C．large animals can also suffer from some kind of wear D．leaf-cutter ants are the most lever ants in the world 小题5:What can be the best title for the passage? A．The key secret to the success of ants B．The developed structure of ant colony C．The most challenging job for leaf-cutter ants D．No V-shaped blade,no success of ants