The most suitable response regarding the cat's motivations advancing the plot would be:
The cat’s determination to be seen a certain way by the other animals causes him to brag about something and set the plot in motion.
This captures the essence of how the cat's motivations lead to the excitement and curiosity among the other animals, setting the stage for the unfolding events in the fable. The cat's need to be admired and seen as knowledgeable causes him to share the information about the beautiful picture, which intrigues the other animals and gets them engaged in the story.