Step 1: First Buddhist Council.
The First Buddhist Council was held just after the death of Buddha in 483 BCE at Rājgir.
It was presided over by Mahākāśyapa and patronized by King Ajātaśatru.
The purpose of this council was to preserve the teachings of Buddha (Dhamma) and monastic rules (Vinaya).
Thus, A → II.
Step 2: Second Buddhist Council.
The Second Council was held about 100 years later at Vaiśālī under the leadership of Revata Thera.
Its main purpose was to settle disputes regarding monastic discipline (Vinaya rules such as use of money by monks).
Thus, B → III.
Step 3: Third Buddhist Council.
The Third Council was convened at Pāṭaliputra under Emperor Aśoka in 250 BCE.
It was presided over by Moggaliputta Tissa.
The aim was to purify the Sangha by removing corrupt and non-Buddhist monks.
Thus, C → IV.
Step 4: Fourth Buddhist Council.
The Fourth Council was held in Sri Lanka at Alu Vihāra under King Vaṭṭhagāmaṇi.
This council is famous because the Tipiṭakas were for the first time written down on palm leaves.
Thus, D → I.
Step 5: Conclusion.
Hence, the correct matches are: (A - II), (B - III), (C - IV), (D - I).