Which of these examples is a strong thesis statement? the strange characters of the looking-glass world are difficult to understand. the strange characters of the looking-glass world emphasize its peculiarity. the strange characters of the looking-glass world are everywhere. the strange characters of the looking-glass world are very interesting.

The 3rd one "The strange characters of the Looking-Glass World are everywhere." because it is the only one that sounds that youcould write a story out of it.

I don't know what the focus of the "essay" is, but I'd have to say the strongest thesis statement would be the second one. You can use the process of elimination to figure it out too.

The third statement would probably not make sense in any typical context, the fourth one is too simple, and the first one is very specific to a certain context. This leaves the second one, which would lead it nicely to an essay about the story.