In the context of medieval India 39 Chola lake 39 refers to the ........

Ancient and Medival History Medieval South Indian History

In the context of medieval India, 'Chola lake' refers to the:

Kallanai dam, which was built across the river Cauvery to divert water for irrigation.

Coromandal coast to suggest the strong trade links of Chola empire with South- East Asia.

Sivaganga tank, which was a rain water harvesting system to collect water for the Brihadiswara temple at Tanjore.

Bay of Bengal to suggest the strong presence of Chola navy.

The Cholas possessed a large army consisting of soldiers, cavalry, archers, and elephants. They had a very powerful and well-organised military force. They were one of the earliest kingdoms to have a navy.
The navy reached to its heights under the Cholas. They took under them the Malabar and Coromandal coasts. With the expansion of Navy and overseas conquest, the Chola Navy became the strongest force in the region. It also monopolized the trade and commerce in Bay of Bengal and parts of Indian ocean. Thus, the Bay of Bengal for sometime became a 'Chola lake'.
Hence, option (d) is the correct answer.