Here's a question and a few possible answers: 

Q: The person was nervously fumbling through the magazines while waiting to be called next, he could hear the whir of machines and instruments in the next room where?
Possible A: airport, bed, library, kitchen, dentist

Why is "dentist" an answer aligned with human common sense? 


dentists would be the only selection which commonly use machines and instruments which create a whirling sound.