A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of foreign aid. It uses the rule of Topic Sentence because it gives a broad overview of the subject. It also uses the phrase 'Beginning in the 1990s,' which sets a chronological context for the discussion. Why other lines are not chosen? Paragraph 2 starts with 'Scrutiny,' which is not an independent sentence because it does not stand alone. Paragraph 3 starts with 'Today,' but it refers to the current situation without context. Paragraph 4 starts with 'Although,' which is a conjunction and cannot be the first sentence.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion. It uses the rule of Conclusive Words, as it reflects on the overall theme of improvement in foreign aid, even if it is not perfect.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because the second paragraph explains how foreign aid improved. It uses the Logical Order rule, as the first paragraph sets the stage for the changes that follow.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because the third paragraph shows the result of the scrutiny mentioned in the second paragraph. It follows the Cause and Effect Relationship rule, where the scrutiny leads to better inspection of projects.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because the fourth paragraph reflects on the current state of the system. It uses the Same Theme rule, as both paragraphs discuss the state of foreign aid and its impact.