Step 1: Understanding the Concept:
The Vedas are broadly divided into two sections: 'Karmakanda' (the section of rituals) and 'Jnanakanda' (the section of knowledge). The Samhitas and Brahmanas primarily focus on rituals, sacrifices, and social duties. The Upanishads, coming at the end of the Vedic corpus, represent the 'Jnanakanda'. Their sole purpose is the investigation of the ultimate truth—the nature of the Supreme Reality (Brahman) and its relationship with the individual soul (Atman). This spiritual science is known as 'Brahma-vidya'.
Step 2: Detailed Explanation:
'Brahma-vidya' literally means the "knowledge of Brahman." The Upanishads declare that all worldly knowledge—arts, crafts, and even the mechanical knowledge of rituals—is 'Apara Vidya' (lower knowledge). The only 'Para Vidya' (higher knowledge) is that which leads to the realization of the Aksara Brahman (the imperishable reality).
Analysis of other options:
- Shilpa-vidya: This refers to the science of architecture, arts, and crafts (one of the Upavedas).
- Karmakanda-vidya: This is the subject of the Brahmanas, focusing on how to perform various sacrifices like the Agnihotra or Soma-yaga to attain heavenly results.
- Yuddha-vidya (Dhanurveda): This is the science of warfare and weaponry.
The Upanishads argue that while rituals lead to temporary rewards in the celestial worlds, only Brahma-vidya can lead to permanent liberation (Moksha) from the cycle of birth and death. The texts use various methods—dialogue, meditation, and logical inquiry—to arrive at the truth that the Atman is identical to Brahman. Statements like "Aham Brahmasmi" (I am Brahman) and "Tat Tvam Asi" (That Thou Art) are the culminating points of Brahma-vidya. In the NTA exam, questions on the 'subject matter' of different Vedic layers are common. The Upanishads are consistently identified with Brahma-vidya, the pinnacle of Indian philosophical thought. This knowledge is intended to remove 'Avidya' (ignorance), which is the root cause of human suffering.
Step 3: Final Answer:
The primary subject of the Upanishads is Brahma-vidya. Therefore, option (1) is correct.