Step 1: Understanding the Concept:
Agricultural extension administration in India is structured into frontline, main/field, and voluntary extension systems.
Step 2: Detailed Explanation:
In India's multi-tiered extension architecture:
1. First-Line (Frontline) Extension System: Managed directly by the research scientists and institutions under the Indian Council of Agricultural Research (ICAR) and State Agricultural Universities (SAUs) (e.g., Krishi Vigyan Kendras [KVKs], National Demonstration Programmes, Frontline Demonstrations [FLDs]).
2. Mainstream Field Extension: Managed by State Departments of Agriculture and Rural Development.
3. Voluntary Sector: Managed by Non-Governmental Organizations (NGOs).
Step 3: Final Answer:
Hence, the first line extension system involves ICAR and SAUs, corresponding to option (A).