Answer:
B) During the prewriting stage.
Step-by-step explanation:
Prewriting is the germinal phase of the writing process where the author begins shaping an idea and thoughts for the essay or paper. The thesis statement exemplifies the central idea and argument of an essay or paper and that is the reason that it should be developed in the prewriting stage to give the readers an idea about the content of the essay. The rest of the essay would include the evidence in support of the argument to persuade the readers to go with the author's claim or thought. Thus, the thesis statement should be developed during this very initial phase as it would assist in providing a dimension to the research and carrying it forward to gather resources to substantiate his central point or argument.