gmat一道逻辑题An overwhelming proportion of the most productive employees at SaleCo’s regional offices work not eight hours a day, five days a week, as do other SaleCo employees, but rather ten hours a day, four days a week, with Friday off.

gmat一道逻辑题An overwhelming proportion of the most productive employees at SaleCo’s regional offices work not eight hours a day, five days a week, as do other SaleCo employees, but rather ten hours a day, four days a week, with Friday off.
gmat一道逻辑题
An overwhelming proportion of the most productive employees at SaleCo’s regional offices work not eight hours a day, five days a week, as do other SaleCo employees, but rather ten hours a day, four days a week, with Friday off. Noting this phenomenon, SaleCo’s president plans to increase overall productivity by keeping the offices closed on Fridays and having all employees work the same schedule—ten hours a day, four days a week.
Which of the following, if true, provides the most reason to doubt that the president’s plan, if implemented, will achieve its stated purpose?
A. Typically, a SaleCo employee’s least productive hours in the workplace are the early afternoon hours.
B. None of the employees who work four days a week had volunteered to work that schedule, but all were assigned to it by their supervisors.
C. Working ten hours a day has allowed the most productive employees to work two hours alone each day in their respective offices relatively undisturbed by fellow employees.
D. Employees at SaleCo are compensated not on the basis of how many hours a week they work but on the basis of how productive they are during the hours they are at work.
E. Those SaleCo employees who have a four-day workweek do not take any of their office work to do at home on Fridays.
答案是c,不懂...请教一下大家

gmat一道逻辑题An overwhelming proportion of the most productive employees at SaleCo’s regional offices work not eight hours a day, five days a week, as do other SaleCo employees, but rather ten hours a day, four days a week, with Friday off.
题目中S公司因为发现生产效率最高的工人都是每天工作10个小时,一周工作四天,而不是向普通工人那样一天工作8小时,一周工作五天.因此S公司决定让所有工人都每天工作10个小时,一周工作四天,以期提高所有工人的工作效率.
C中说那些每天工作10个小时,一周工作四天的工人之所以工作效率高是因为在每天比别人多工作的那两个小时里可以专心工作不被别人打扰.如果大家都变成每天工作10个小时,一周工作四天的话,人和人之间就会相互打扰,这就削弱了原文S公司计划成功的可能性.