A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text. It clearly states what vegetarians do not eat. This is a general statement that does not need other sentences for context. It does not start with a conjunction or use pronouns. It also does not use the definite article 'the' for defined subjects. Why other lines are not chosen? The other paragraphs are not chosen because they do not meet the criteria for being independent. For example, Paragraph 2 starts with 'This diet,' which refers back to the diet mentioned in the first sentence. Paragraph 3 starts with 'Restaurants,' which is too specific and does not stand alone. Paragraph 4 starts with 'Menus,' which also does not stand alone. Paragraph 5 starts with 'These developments,' which refers back to earlier ideas.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main ideas of the text. It shows that the changes in menus depend on the efforts of vegetarians. This brings together the earlier points about vegetarian diets and menu changes.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it talks about the diet of vegetarians. It uses the word 'diet' which links back to the first paragraph. This shows a logical order from the definition of vegetarians to the problems of their diet.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it talks about how restaurants and cafeterias change their menus. This shows a logical order from discussing the problems of the diet to how places adapt to it.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains how menus have changed. It shows a logical order from how restaurants adjust their menus to how those menus are now more balanced.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it talks about the success of these menu changes. It shows a logical order from how menus attract more people to the need for vegetarians to support these changes.