Answer:
(B) The thesis statement is the sentence in the introduction that states the author's specific ideas about the topic.
Explanation:
A thesis statement is meant to tell the reader what the rest of what they're reading will be about.
(A) is wrong because the thesis needs some context so that the reader can understand it; therefore, the first sentence of the writing is too soon to state a thesis.
(C) Each body paragraph relates to one of the author's ideas, so the topic sentence would only introduce that one idea and not the others, meaning it cannot be our thesis statement.
(D) is wrong because we want our thesis to be placed before the meat of any piece of writing as an explanation of what's to come. While you often reword your thesis in a conclusion, that is not the thesis statement because it is at the end, serving no purpose other than to reiterate the author's ideas.