Step 1: Understand the term "Mahajanapada" and the question's context.
The Mahajanapadas were sixteen great kingdoms or republics that existed in ancient India from the sixth to fourth centuries BCE. Each had a significant city or region as its capital. The question asks to identify the Mahajanapada whose capital was Kotilingala.
Step 2: Recall the capitals of the given Mahajanapadas.
Avanti: Its capital was Ujjain (or Mahishmati), located in present-day Madhya Pradesh.
Magadha: Its initial capital was Rajagriha (modern Rajgir), later shifted to Pataliputra (modern Patna). It was one of the most powerful Mahajanapadas.
Asmaka (or Assaka): This was the only Mahajanapada located in South India, on the banks of the river Godavari. Its capital cities were Potana or Potali. Historical and archaeological evidence suggests that Kotilingala, a site on the banks of the Godavari in Telangana, served as an important early capital or a significant urban center for the Asmaka Mahajanapada, especially during the early Satavahana period who rose from this region.
Panchala: This Mahajanapada had two capitals: Ahichchhatra for Northern Panchala and Kampilya for Southern Panchala, located in present-day Uttar Pradesh.
Step 3: Conclude the correct Mahajanapada.
Based on historical information, Kotilingala is associated with the Asmaka (Assaka) Mahajanapada.