The correct answer is D. Thesis
Step-by-step explanation:
An essay is an academical paper, written with the purpose of providing arguments and evidence to support a thesis or main claim in relation to some subject, and after researching or gathering information. Because of this, these papers are usually organized in an introduction, body paragraphs and conclusion structure. The introduction or opening paragraph, in this the main subject or topic is presented along with the thesis statement or main claim that guided the research process and the ideas in the essay. After this, the body paragraphs explain and support through evidence and arguments the thesis and finally the final paragraph or paragraphs serve as a closure for the essay. Therefore, the element of the research process that will appear in the opening paragraph of an essay is the thesis or thesis statment.