Do artists have an obligation to tell the truth? why or why not ? pick an artwork and tell how it does or does not tell the truth

No they don't, because there is a lot of techniques that they can use depending on the way they want to represent the basic idea. For example using pointilism, the world is not a lot of points, but the focusing was in the correct light representation (Pos-impressionism period) so it's not the truth but the way the artist judges that. A better way to example it is the surrealism, where the main idea is to make some crazy things.

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