Step 1: Conceptual Understanding:
The objective is to align the Niyamas, the second of the eight limbs of yoga as per Patañjali's Yoga Sūtras, with their corresponding English definitions.
Step 2: Detailed Analysis:
Each Niyama from List-I will be defined and matched with its description in List-II.
(A) Śauca: Encompasses purity and cleanliness, both external (physical) and internal (mental, verbal, and thought processes). This aligns directly with (I) Purity of body, mind, thought.
(B) Santoṣa: Signifies contentment. It involves accepting and appreciating one's current situation, avoiding desire for what is lacking. This corresponds perfectly to (II) Positive Contentment.
(C) Tapas: Refers to austerity, self-discipline, and the spiritual effort or "heat" that purifies the body and mind, fostering willpower. This matches precisely with (IV) Austerity.
(D) Svādhyāya: Means self-study or introspection, including the examination of sacred texts leading to self-realization. This aligns exactly with (III) Self-study, introspection.
Step 3: Conclusion:
The established pairings are as follows:
A - I
B - II
C - IV
D - III
This combination corresponds to option (2).