Which statement best shows the difference between an essay’s theme and the author’s purpose?

The author’s purpose is the message the author wants to convey, while the theme is the author’s reason for writing.
Themes are always meant to persuade readers of an opinion, while the author’s purpose is never to persuade.
Themes are statements that can be proven true, while purposes are opinions that cannot be supported.
The theme is the message the author wants to convey, while the purpose is the author’s reason for writing.