The correct answer is B. During the prewriting stage
Step-by-step explanation:
In essays, the thesis statement is an essential element because this expresses the point the author of the essay is trying to prove, and therefore it is a guide for writing in the essay. In this context, Peter needs to define the thesis statement before he begins to write, this is during the prewriting stage. Also, during this Peter will need to select the evidence to support the thesis, and decide how to organize the text because you cannot begin to write without these elements. Also, stages such as drafting, editing, or revising occur after the prewriting stage. Thus, it is the prewriting stage the one in which Peer needs to develop his thesis statement.