Answer:
<em><u>(B.) The main reason people are quitting smoking are that it increases the risk of lung cancer, its offensive to others and it's very expensive</u></em>
Explanation:
Found in the introductory paragraph, a <u>thesis statement</u> establishes the <u>main ideas</u>, points or elements that are going to be discussed and analyzed in an essay or article's body paragraphs.
Option B is the best <u>thesis statement</u> because it presents concise and specific information that can be thoroughly discussed in three paragraphs, which illustrate the essay's main topic: <em>reasons why people are quitting smoking</em>.
The remaining options are not good <u>thesis statements</u> because they do not offer multiple and specific ideas considerable for an analysis or discussion.