HELP what is the main idea of this paragraph​

The main idea of this paragrph is the concept of medium of exchange.

Explanation:

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people began using shells as a medium of exchange

usually, a falcon can kill an owl, and horses don't normally eat each other.

you can change by someone having a negative opinon of you in many ways for example thi can lead to depression and taking of ones life also known as sucide this effects there self esteem and ego in a negative way making them feel sad depressed and stressed causing them to act gloomy and sad if this continuses this can lead to self harm or much worse things.

hope i .