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 origins of major groups in evolution. It does not refer to any previous information, making it an independent sentence. It sets the stage for the discussion about fossils and evolution. Why other lines are not choosen? The other paragraphs are not chosen because they either start with conjunctions, use pronouns, or refer back to previous ideas. For example, Paragraph 2 starts with 'Today,' which suggests a time reference that needs context. Paragraph 3 starts with 'Others,' which refers back to a previous idea. Paragraph 4 starts with 'An evolving group,' which also needs prior context.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion about evolution and adaptation. It provides examples of how evolution can happen, which brings together the earlier points made in the text.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): The second paragraph connects to the first because it continues the discussion about evolution and transitional forms. It uses the logical order of ideas, moving from the argument about origins to the belief about the rate of evolution.
• Pair 2 (Paragraph 2 → Paragraph 3): The third paragraph connects to the second because it presents a contrasting view. It uses the connector 'Others, however,' to show that there are different beliefs about evolution, linking the two ideas.
• Pair 3 (Paragraph 3 → Paragraph 4): The fourth paragraph connects to the third because it explains how evolution can happen in spurts. It continues the topic of evolution and provides examples of how groups may adapt, showing a logical flow of ideas.
• Pair 4 (Paragraph 4 → Paragraph 5): This pair does not connect to another paragraph because it is the last paragraph. It concludes the discussion about evolution and how groups adapt to changes in their environment.