What does the Barnum effect demonstrate?

Circus owners have excellent skills for detecting true personality traits.

People are willing to believe interpretations about themselves.

People are easy to swindle.

A person should be cautious about spending time at the wrong events.

I believe the answer is: People are willing to believe interpretations about themselves.

According to Barnum effect, even if we make an interpretation that vague and general enough to apply to a wide range of people and say it to a specific person, that specific person would most likely see it as true and believe the people who give the interpretation.