请教一个狒狒笔记中的逻辑题

shuishuiles

Child's World, a chain of toy stores, has relied on a supermarket concept of computerized inventory control and customer self-service to eliminate(消灭) the category of sales clerks from its force of employees. It now plans to employ the same concept in selling children's clothes.
The plan of Child's World assumes that
(A) supermarkets will not also be selling children's clothes in the same manner
(B) personal service by sales personnel is not required for selling children's clothes successfully
(C) the same kind of computers will be used in inventory control for both clothes and toys at Child's World
(D) a self-service plan cannot be employed without computerized inventory control
(E) sales clerks are the only employees of Child's World who could be assigned tasks related to inventory control

答案是B，为啥不是D呢？知道的请给个解释，谢啦！