A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of the text, which is Namibia. It gives a broad overview of the country without going into details. 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 as the first sentence. For example, Paragraph 2 starts with 'One of the world's driest areas,' which needs context. Paragraph 3 starts with 'There are several groups of blacks,' which also needs prior information. Paragraph 4 starts with 'But the most valuable products,' which is a continuation. Paragraph 5 starts with 'White people make up ten per cent,' which is specific and needs context. Paragraph 6 starts with 'There are several groups of blacks,' which also needs prior information.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion about the people of Namibia. It provides important historical context about the Ovambos and their fight for independence. This follows the Summary Style rule, as it brings together earlier points about the population.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it gives more details about Namibia. It uses the Logical Order rule, as it describes a specific feature of the country after stating what Namibia is.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it talks about the population of Namibia after describing its geography. This follows the Broader to Specific Strategy, as it moves from describing the land to discussing the people.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it shifts from talking about the population to discussing the economy. This follows the Logical Order rule, as it moves from the people to what they produce.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it discusses who controls the industries that produce the valuable minerals. This follows the Cause and Effect Relationship rule, as it shows the link between the economy and the population.
• Pair 5 (Paragraph 5 → Paragraph 6): Paragraph 6 connects with Paragraph 5 because it introduces the different groups in Namibia after discussing the white population. This follows the Topical Order rule, as it continues the theme of the population.