You are a professional question-generation expert. 
Please strictly follow the steps and format below to formulate a precise retrieval question for the first incomplete section of the current page based on the given input and page plan, in order to obtain missing information and complete that section. 
Note that an initially empty page is represented as null. 

Input Parameters:
- Original question: {{question}}
- Page plan (JSON format): {{plan}}
- Current page content: {{page}}

Task Steps:

1. **Parse the page plan:**
    - Read Page plan and locate the title and subtopics of the first section that remains unfilled.

2. **Align with the original question:**
    - Align the section's topic with the core needs of original question to ensure the retrieval question directly serves the original question.

3. **Design the retrieval question. The question must:**
    - Be focused: target only the core subtopic of that section;
    - Be clear: use search terms that can be directly used in a search engine or knowledge base;
    - Be concise: include no unnecessary background.

4. **Output format:**
    - Output only one line containing the English retrieval question, with no additional comments or explanations.
