Research was done to study the facial expressions of people, since facial expression clearly shows the emotional state of a person. Researchers found that people who smiled a lot lived longer than those who didn't smile much.

Which statement can be inferred from the passage?


Smiling prolongs human life.



Smiling is associated with human longevity.



Smiling decreases a person's life span.



There is no link between smiling and human longevity.