Which of the Following Is an Example of a Poka-Yoke

Which of the following is an example of a poka-yoke?

A) Lynsey is so upset with the service she got at the travel agency that she is launching a one-woman campaign to put it out of business
B) The business owner complains to the licensing board every time the next-door restaurant's employees forget to put the lids on the garbage cans
C) The day care center has carefully labeled bins for each parent to fill with food,diapers,clothes and toys so that one child's stuff will not be confused with another's
D) The customer refused to pay the delivery fee because the package arrived two days late
E) The dentist's office staff regularly does lose customer research