Step 1: Understanding padārthas in Vaiśeṣika.
Vaiśeṣika philosophy classifies reality into padārthas such as Dravya (substance), Guṇa (quality), Karma (action), Sāmānya (generality), Viśeṣa (particularity), and Samavāya (inherence).
Step 2: Evaluating the options.
Guṇa is explicitly one of the six classical padārthas.
Ātman, Tejas, and Vāyu are classified as substances (dravya), not categories themselves.
Step 3: Conclusion.
Hence, Guṇa is the correct example of a padārtha.
Final Answer: (A)