Step 1: Rigveda.
Associated with Kaushitakyopanishad. Hence A - III.
Step 2: Shukla Yajurveda.
Associated with Ishavasyopanishad. Hence B - IV.
Step 3: Krishna Yajurveda.
Associated with Taittiriyopanishad. Hence C - I.
Step 4: Atharvaveda.
Associated with Prashnopanishad. Hence D - II.
Step 5: Conclusion.
Thus, the correct match is A - III, B - IV, C - I, D - II.