Step 1: Understanding the Concept:
The Aitareya Brahmana is divided into 40 chapters, which are further grouped into units of five called Panchikas. This question requires the student to know the exact location of the most famous narrative in the entire Rigvedic ritual tradition—the story of King Harishchandra and the boy Shunahshepa. Identifying the opening lines (Pratikas) of major sections is an advanced way the NTA tests textual literacy.
Step 2: Detailed Explanation:
The legend of Shunahshepa is situated in the 33rd chapter (Trayastrimsha Adhyaya) of the Aitareya Brahmana.
1. Calculation of the Panchika: Since each Panchika contains 5 chapters, the mapping is:
- Panchika 1: Ch. 1-5
- ...
- Panchika 6: Ch. 26-30
- Panchika 7: Ch. 31-35
Therefore, chapter 33 falls squarely within the Seventh (Saptama) Panchika. This Panchika is primarily concerned with the Rajasuya sacrifice (Royal Consecration). The Shunahshepa legend is a mandatory recitation during the Rajasuya because it highlights the divine grace needed for a king to have a lineage (progeny).
2. The Narrative Context: The story begins with the quoted line: "Hariścandro ha vaidhāsa aikṣvāko rājā-aputro babhūva." It describes how the king, despite having a hundred wives, had no son. He then prayed to the god Varuna, promising to sacrifice his first-born if he were blessed with a son. This "Broken Vow" leads to the eventual substitution of the king's son, Rohita, with the Brahmin boy Shunahshepa.
3. Importance for Exams: The Shunahshepa legend is significant because it appears in multiple layers of Vedic and Epic literature (Ramayana, Mahabharata), but the Aitareya Brahmana version (7.33) is considered the oldest and the most authoritative. Knowing that the "Story section" starts at the 33rd chapter in the 7th Panchika is a recurring high-yield fact for Sanskrit competitive examinations. The first six Panchikas are mostly technical ritual instructions, whereas the 7th and 8th Panchikas shift towards narratives and royal coronations.
Step 3: Final Answer:
The story of Harishchandra/Shunahshepa begins in the Seventh Panchika (Saptama-panchikayam). Therefore, option (3) is correct.