A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of education. It gives a broad overview of traditional education without going into details. It does not use any pronouns or definite articles that need prior context. Why other lines are not chosen? Paragraph 2 starts with "However," which is a conjunction, so it cannot be independent. Paragraph 3 starts with "Online courses," which is specific and assumes prior knowledge. Paragraph 4 uses "the primary mode," which refers back to the previous context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about online education. It summarizes the benefits of online learning, showing how it helps people with different commitments.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 using the Connector strategy. The word "However" shows a contrast between traditional education and the new way of learning through the internet.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 follows Paragraph 2 logically. It uses the Broader to Specific strategy. Paragraph 2 talks about the internet's impact, and Paragraph 3 gives a specific example of that impact: online courses.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 using the Logical Order strategy. It continues the idea of online education by explaining how it offers flexibility, which is another benefit.