When a motif gains larger significance throughout a text, it becomes a theme, something larger that you talk about in your work. But since theme is not a listed option, I would say the correct answer is 5) a thesis.
The <em>repetition of a specific theme dominanting</em> of things that have a significance in a literary work is what this literay device, motif, is about. It helps to develop the central theme. And, being a <em>recorring </em>element, it can be used as a <em>reminder of certain ideas</em> for the readers; <em>it's like the claim or main argument about a topic.</em>
