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 _ . 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 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 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 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. The younger and stronger ants do the toughest job because  _  .
they can teansport the leaves effectively they have a sharp blade to cut leaves other members are busy with other work they can finish the job in a better organized way
Question: 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 _ . 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 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 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 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. 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
Answer: