Answer:
D). Sentence 4.
Explanation:
The topic is illustrated as the subject or theme that has been centrally discussed or argued in a paper or text.
In the given excerpt, sentence 4 displays the topic of the paragraph as the idea 'Heroes today, unlike those of the past, must have a flawed character in order to become popular' primarily functions to indicate the key concern(subject) of the paragraph that proposes a universal approach to which the readers could affiliate and that binds all the elements of the paragraph in a single thread in order to offer an accomplished thought. Therefore, it reflects the theme of the paragraph and hence, option D i.e. sentence 4 is the correct answer.