First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of nuclear fission and atomic power stations. It does not need other sentences for context. It sets up the main idea without going into details. Why other lines are not chosen? Paragraph 2 starts with 'In Britain,' which needs context. Paragraph 3 starts with 'Subsequently,' which shows it follows something else. Paragraph 4 starts with 'Of necessity,' which also needs prior information.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about nuclear power stations. It explains the reasons for their location, which brings together the main ideas of the text.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives a specific example of atomic power stations. This is a 'Broader to Specific Strategy.' The first sentence talks about the general idea, and the second gives a specific case.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 follows Paragraph 2 because it continues the idea of nuclear power stations. The word 'Subsequently' shows that this is the next step after Calder Hall. This is a 'Chronological Order' connection.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains why nuclear power stations are built near water. This is a 'Cause and Effect Relationship.' The planning of power stations leads to the need for specific locations.