A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of mobile technology. It gives a broad overview of the start of mobile technology with 2G. It does not use any pronouns or definite articles that refer to previous information. Why other lines are not chosen? Paragraph 2 starts with "Progressing to 3G," which refers to the previous topic and is not independent. Paragraph 3 starts with "The advent of 4G," which uses the definite article "the" and assumes prior knowledge. Paragraph 4 starts with "With the introduction of 5G," which also refers back to previous information.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it concludes the discussion on mobile technology. It summarizes the advancements made with 5G and reflects the overarching theme of progress in mobile technology.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 logically connects with Paragraph 1 because it continues the topic of mobile technology. It follows the logical order of progression from 2G to 3G.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it shows the next step in mobile technology. It follows the logical order of progression from 3G to 4G.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it continues the topic of mobile technology. It follows the logical order of progression from 4G to 5G.