Hey there!
In Their Eyes Were Watching God, Hurston writes her characters as having very informal dialect with one another that reflects the southern roots of Janie and the other characters she interacts with.
For example, instead of "I didn't know you were home", Hurston writes "Ah didn't know you wuz home," utilizing "Ah" instead of "I" and "wuz" instead of "were".
Their Eyes Were Watching God wasn't about Hurston herself, but she did write Janie's character and story based on her own experiences, especially those growing up. During her narration, she writes in a relatively formal way since she has learned to become a writer who prefers that form of writing over others, but has her characters use a much less formal dialect when conversing with one another, as she experienced herself throughout her life.
Your answer will be your fourth option.
Hope this helped you out! :-)
