A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of human geography. It gives a broad overview of what human geography is. It does not refer to any previous information. Why other lines are not chosen? Paragraph 2 starts with 'It', which is a pronoun and needs context. Paragraph 3 starts with 'It developed', which also needs prior information. Paragraph 4 starts with 'He used', which refers to a person not mentioned before.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the ideas about human geography. It gives a conclusion about how landscapes and cultures are connected.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it explains what human geography studies. This is a Broader to Specific Strategy, where the first paragraph gives a general idea and the second paragraph gives specific details.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it tells where human geography started. This shows a Logical Order, as it moves from what human geography studies to where it developed.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it explains what Professor Carl Sauer did in human geography. This is an Object Subject Strategy, where the subject of the third paragraph becomes the focus of the fourth paragraph.