First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of noise levels in the workplace. It does not refer to any previous information and sets the stage for the discussion. It is a general statement about noise and its effects. Why other lines are not chosen? Paragraph 2 starts with 'This' which is a pronoun and needs context. Paragraph 3 starts with 'Besides' which is a conjunction and cannot be first. Paragraph 4 starts with 'Therefore' which also shows it is not independent.

Concluding sentence: Why this is the last line? This paragraph is the last line because it gives a conclusion and suggests actions to take. The word 'Therefore' shows that it wraps up the discussion about noise and its effects.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains the effect of high noise levels. It uses the connector 'This' to show that it is a result of the previous statement.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it adds more information about the effects of noise. The word 'Besides' shows that it is giving additional details about the problems caused by noise.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it suggests a solution to the problems mentioned. The word 'Therefore' shows that it is a conclusion based on the previous information.