On “ a call loan” what’s the purpose of paragraph 1-3

It should be noted that the central idea is that the foods offered in American supermarkets are very convenient but unhealthy.

A central idea simply means the theme or the main idea that's in a story. It's simply the reason why the author writes the literary work.

In this case, the main idea is that the foods offered in American supermarkets are very convenient, but unhealthy. It was stated that canned foods are unhealthy and can lead to diseases.

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