A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of short-term memory. It gives a broad overview of what short-term memory is. It does not use any pronouns or definite articles that would need prior context. Why other lines are not chosen? The other paragraphs are not chosen because they do not meet the criteria for being independent. For example, Paragraph 2 starts with 'According to', which is a reference phrase. Paragraph 3 starts with 'However', which is a conjunction. Paragraph 4 starts with 'It is', which uses a pronoun that refers back to something not yet mentioned.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about short-term memory and how we remember things. It summarizes the main idea and gives a clear conclusion about the process of rehearsal.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it gives more specific information about short-term memory. This follows the Broader to Specific Strategy.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it introduces a new idea about how we can remember information. The word 'However' shows a contrast, linking the two ideas.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it explains the process mentioned in Paragraph 3. The phrase 'It is a process' shows that this paragraph gives an example of what was just discussed.