Final answer:
The second and third sentences of an introduction usually summarize the text or texts being discussed, hence the correct option is B summary. These sentences provide the necessary background to inform the reader about the content and context of the essay.
Step-by-step explanation:
The second and third sentences of an introduction typically serve to provide context or background for the essay, which can include summarizing the text or texts you will be discussing. This would be aptly described as a summary (Option B) of the content. These sentences help set the stage for the reader by elaborating on what has been said about the topic or by offering historical context, depending on the essay prompt.
In contrast, a claim (Option D) is a specific assertion that the essay will argue to be true, and is typically derived from the thesis statement. The claim is supported throughout the essay by evidence and analysis, which explains how the evidence supports the claim. While 'justifications' and 'premise' are also important to an essay's argument, they do not accurately describe the summarizing function of the second and third sentences in an introduction.