The standard policy of the mail delivery system of Bainsbury is to hold registered mail at the post office and ask the intended recipients to drive to the post office in order to retrieve it. Last year, this policy generated long waits at the post office, due to the fact that government tax returns are all delivered on the same day by registered mail, as are many holiday cards and packages, and the post office was flooded with visitors. The post office is expecting the same amount of registered mail on the day that government tax returns are delivered this year as it received on the corresponding day of last year. In order to reduce the wait time at the post office on such days to half of what it was last year, the post office has changed its policy. This year, the post office will take half of the bags of registered mail on tax days and holidays and deliver their contents by hand to their intended recipients.

Which of the following must be true for the post office's plan to achieve its goal on days with unusually high quantities of registered mail?

A
Delivering half of the registered mail received on holidays will cost the Bainsbury post office no more than delivering non-registered mail on days with regular mail volume.
B
This year, every piece of registered mail that is being held at the post office must be addressed to a recipient for whom no other piece of registered mail is being held at the post office.
C
The average number of visitors to the post office per bag of registered mail delivered this year will be no higher than the average number of visitors to the post office per bag of registered mail delivered last year.
D
Registered mail delivered to Bainsbury will constitute a smaller percentage of all mail delivered this year than it did last year.
E
The total number bags of registered mail delivered to Bainsbury this year will be smaller than the total number of bags of registered mail delivered to Bainsbury last year.