First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic about mules in the smuggling business. It gives a broad overview of their situation without going into details. It does not use any words that need prior context. Why other lines are not chosen? Paragraph 2 starts with "A mule probably..." which is not independent because it uses the definite article "the". Paragraph 3 starts with "Although..." which is a conjunction, so it cannot be first. Paragraph 4 starts with "He will be told..." which uses a pronoun and needs context. Paragraph 5 starts with "To make identification..." which is not a general statement.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion about mules. It introduces a new idea about identification, which is a good way to end the text. It gives a clear conclusion to the topic.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the idea of mules. It explains more about the mules and their lack of knowledge about their contacts. This shows a logical order of ideas.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it explains what happens next for the mule. It shows the process of what the mule does after receiving instructions. This is a logical order of events.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it describes what the person at the receiving end does. It follows the actions of the mule and shows the next step in the process. This is a logical order.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it introduces a new idea about how to identify mules. It shows a broader topic about mules and their identification, which follows the previous discussion about their actions.