She tells them that she will give the student who skips the quiz whose name comes first alphabetically a detention.
This student won't skip because they know they are getting a detention if they do.
The next person alphabetically will then know that they will get a detention so they won't skip either, and so on.
Answer:- The police officer suspects the newspaper delivery person. The absence of Tuesday's and Wednesday's newspaper indicates that the delivery person knew there was no one there to read it.