Step 1: Rigveda.
Corresponds to Kaushitakyopanishad. Therefore, A - III.
Step 2: Shukla Yajurveda.
Corresponds to Ishavasyopanishad. Therefore, B - IV.
Step 3: Krishna Yajurveda.
Corresponds to Taittiriyopanishad. Therefore, C - I.
Step 4: Atharvaveda.
Corresponds to Prashnopanishad. Therefore, D - II.
Step 5: Conclusion.
The correct matching is A - III, B - IV, C - I, D - II.