First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text. It talks about how researchers can limit a study. This is a general statement that does not need other sentences for context. It does not use any pronouns or specific articles that refer to previous ideas. Why other lines are not chosen? Paragraph 2 starts with 'This will enable...' which uses a pronoun that refers back to the first sentence, so it cannot be independent. Paragraph 3 starts with 'The most common...' which uses 'the' to refer to a specific method, needing prior context. Paragraph 4 starts with 'These intervals...' which uses 'these' to refer back to something mentioned before. Paragraph 5 starts with 'For example...' which shows it is giving an example and needs prior context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it gives a specific example that wraps up the discussion about sampling methods. It does not introduce new ideas but shows how the method can be applied in practice.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains the benefit of using a specific sampling method. This shows a cause and effect relationship. The first sentence talks about limiting the study, and the second sentence explains how this helps gather data.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it gives a specific method that helps gather data. This follows the Broader to Specific Strategy. The second sentence talks about gathering data, and the third sentence explains the common method used to do this.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives more details about the intervals used in time sampling. This shows a Logical Order where the third sentence introduces the method, and the fourth sentence explains the types of intervals.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it gives an example of the intervals mentioned. This follows the Topic Example rule, where the fourth sentence talks about intervals, and the fifth sentence provides a specific example of how to use them.