A good thesis is 1. It is not a title, a question or a phrase. The thesis should not suggest two or more different ideas. It should state an opinion, not a fact, nor a personal preference.
Word choice is particularly important in a thesis sentence.
Key words should be carefully selected and used throughout the paper for coherence. Anticipating a method of development can help finding the focus of the paper and shaping the thesis. The thesis can help planning the outline or vice versa. Make the thesis statement a simple or a complex sentence. A compound sentence will not be unified because it communicates two ideas.