The best answer to the question 'What does every paragraph in an essay should have?" would be letter a. In an essay, there should be a topic sentence that states the main idea. This main idea should be conveyed with supporting paragraphs in order for the reader to fully understand the message.
Usually, the basic rule of writing an essay is to divide the essay into three parts, introduction, body, and conclusion. The paragraphs include pointing the main ideas and mentioning them in the essay. The topic sentence contained in the paragraph focuses on what the paragraph is all about. The inclusion of examples and evidence in support of it helps in emphasizing the main idea.
Situational irony is a literary device in which the outcome is unexpected: the result is unpredicable or the opposite occurs instead. For example: "The bus driver has failed the driving test," or "The cook has burnt the chicken."