Arrange the following in descending order (backward) starting from the recent…

Concept

Sequencing early Indian history rests on the established timeline of technology, urbanisation and regional cultures. "Descending (backward) order from the recent period" means listing the events from the most recent to the oldest, so the latest development is placed first and the earliest last.

Application — dating each event

• Beginning of the use of iron in the subcontinent — the earliest of the four, roughly 1200–1000 BCE (the early Iron Age / Painted Grey Ware horizon).

• Increase in the use of iron, growth of cities and punch-marked coins — the second urbanisation of the Ganga plains, around the 6th century BCE (Mahajanapada / NBPW period), clearly later than the first appearance of iron.

• Beginning of the composition of Sangam literature — the early historic Sangam age, roughly 300 BCE onward, after iron-using cities and coins were already established in the north.

• Settlement at Arikamedu port — the indo-Roman trade settlement of the 1st century BCE–2nd century CE, the most recent of the four.

Result

Oldest to newest the sequence is: early iron → iron-age cities and coins → Sangam literature → Arikamedu port. Reading it backward (most recent first) gives the order C, D, A, B.

Cross-check

Arikamedu's Roman contact is firmly early historic (turn of the Common Era), which must come after the Sangam corpus had begun; both clearly post-date the punch-marked-coin urbanisation, which itself post-dates the very first iron use. The chronology is internally consistent, confirming C, D, A, B.