All kindergartens face the same problem: For parents who cannot pick up their children in time after school, the kindergarten teacher has no choice but to wait, so many kindergartens charge fees to parents who pick up their children late. However, there are surveys It shows that the number of parents who pick up their children late after charging fees has not decreased, but has increased. Which of the following, if true, would best explain the findings? ['the fee is too low, and it is not too binding on parents who often come to pick up children late.', 'some parents are dissatisfied with the charging behavior, sometimes they willfully protest with the behavior of picking up their children late.', 'some parents are often unable to pick up their children in time because of busywork.', "After charging, more parents think that they don't need to feel guilty even if they pick up their children late, just pay."]