Many large department stores in Montalia now provide shopping carts for their customers. Since customers using shopping carts tend to buy more than those without shopping carts, most of these stores are experiencing strong sales growth, while most other department stores are not. Therefore, in order to boost sales, managers of Jerrod's, Montalia's premier department store, are planning to purchase shopping carts and make them available to the store's customers next month.
Which of the following, if true, casts most doubt whether the managers' plan, if implemented, will achieve its goal?
【选项】Stores that make shopping carts available to their customers usually have to hire people to retrieve the carts from parking areas.
选项是否正确？