First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic about the size of ant communities. It gives a broad overview without going into details. It does not use any pronouns or definite articles that need prior context. Why other lines are not chosen? Paragraph 2 starts with 'And', which is a conjunction. Paragraph 3 uses 'However', which is also a conjunction. Paragraph 4 starts with 'I', which is a pronoun. Paragraph 5 uses 'It', which is a pronoun. All these sentences cannot stand alone without context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main idea. It gives a conclusion about how ants recognize each other, which reflects the overall theme of the text.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it uses 'And' to show a continuation of thought. It gives a lesson about the behavior of ants in the same community.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 using 'However' to show contrast. It explains that while ants do not fight within their community, they are hostile to other communities.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives an example of the hostility mentioned. It shows a specific case of ants attacking each other.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it summarizes the idea that ants recognize each other. It concludes the thought about their behavior.