A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of the painting process. It talks about choosing the colour, which is important before starting to paint. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with "Before the actual painting began," which needs context from a previous sentence. Paragraph 3 starts with "The transformation began," which also needs earlier information. Paragraph 4 starts with "Finally," showing it is not independent.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the painting process. It uses the word "Finally," which signals the end of the steps. It also summarizes the final result of the painting.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it shows the next step after deciding on the colour. The use of "Before" shows a logical order of actions in the painting process.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows what happens after preparing the area. The phrase "The transformation began" indicates a logical order in the painting steps.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows the next step after applying the primer. The word "Finally" indicates that this is the last step in the process.