A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of biomes. It gives a clear definition of what a biome is. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs do not qualify as the first sentence. - Paragraph 2 starts with 'There are', which is not independent. - Paragraph 3 starts with 'As the most significant biome', which is not independent. - Paragraph 4 starts with 'Freshwater biomes', which is not independent. - Paragraph 5 starts with 'On the other hand', which is not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about biomes. It gives a final detail about marine biomes. This follows the Conclusive Words rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it gives more information about biomes. This follows the Broader to Specific Strategy. The first paragraph talks about what a biome is, and the second paragraph lists the types of biomes.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it focuses on one type of biome, which is aquatic. This follows the Broader to Specific Strategy. The second paragraph lists all types of biomes, and the third paragraph talks specifically about aquatic biomes.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives more detail about one part of aquatic biomes, which is freshwater. This follows the Logical Order rule. The third paragraph introduces aquatic biomes, and the fourth paragraph explains freshwater biomes.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it talks about another type of aquatic biome, which is marine. This follows the Logical Order rule. The fourth paragraph explains freshwater biomes, and the fifth paragraph introduces marine biomes.