Step 1: Understanding the Concept:
This question focuses on mass or group contact methods used in extension work to share technical information with rural communities.
Step 2: Detailed Explanation:
Let us analyze each of the written and spoken communication methods listed:
1. Script of a radio program:
While this contains structured information, it is an audio-based broadcast medium, not a written text document sent directly to individuals.
Thus, Option (A) is incorrect.
2. Newspaper:
This is a general mass-circulation publication produced by commercial organizations, not a personalized document sent by an extension officer to a specific target community.
Thus, Option (B) is incorrect.
3. Bulletin Board:
This is a static display placed in a central location (such as a community center or panchayat office).
It requires people to visit the board to read the information, rather than being sent directly to them.
Thus, Option (C) is incorrect.
4. Circular Letter:
This is a written communication prepared by an extension officer and sent directly to many members of a community at once.
It carries uniform, authoritative information (e.g., advising farmers on pest prevention steps ahead of a specific season).
Because it is delivered directly to community members, it has high personal credibility and a strong potential to influence behavior.
Step 3: Final Answer:
The given definition describes a Circular Letter.
This matches Option (D).