Concept:
The sixth century BCE witnessed the emergence of sixteen major territorial states known as the Mahajanapadas across the Indian subcontinent.
These states stretched from the northwestern frontier across the Indo-Gangetic plains southward to the Deccan plateau.
Geographical alignment of these early states requires mapping their historical capitals and territorial domains from north to south.
Step 1: Identifying the Geographic Locations of the Given States:
1. Gandhara (C): Located in the extreme northwest of the subcontinent, covering modern Peshawar, Rawalpindi, and Taxila (Khyber Pakhtunkhwa and northern Punjab). This is the northernmost state among the four.
2. Matsya (B): Located in the region of modern Rajasthan, centering around modern Jaipur and Alwar, with its capital at Viratnagar.
3. Avanti (D): Located in central India, covering the Malwa plateau region in modern Madhya Pradesh, divided into northern and southern sectors with capitals at Ujjain and Mahishmati.
4. Ashmaka Assaka (A): Located in peninsular India on the banks of the river Godavari, around modern Maharashtra and Telangana, with its capital at Potana or Bodhan. It is the southernmost Mahajanapada.
Step 2: Arranging from North to South:
Moving from the far northwest downwards to peninsular India gives:
Gandhara (C) $\rightarrow$ Matsya (B) $\rightarrow$ Avanti (D) $\rightarrow$ Ashmaka (A).
This corresponds precisely to the alphabetical sequence C, B, D, A.
Final Answer:
The correct north-to-south arrangement of the early states is C, B, D, A.