A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it makes a general statement about observation. It does not need another sentence for context. It introduces the main idea without specifics. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'Every act...' which is not independent. Paragraph 3 starts with 'All scientific work...' which also needs context. Paragraph 4 uses 'This expectation...' which refers back to something. Paragraph 5 starts with 'Hypotheses provide...' which also needs prior information.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about hypotheses. It summarizes the main points and shows their importance in scientific work. This follows the Summary Style rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains what is meant by 'unbiased observation'. This follows the Logical Order rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows how our past experiences lead to expectations in scientific work. This follows the Broader to Specific Strategy.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it defines what the expectation is. This follows the Topic Example rule.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it explains the role of hypotheses in scientific inquiry. This follows the Logical Order rule.