Kolleru Lake is located between the Krishna and Godavari delta in India. It is one of the largest freshwater lakes in the country and serves as an important habitat for a wide variety of flora and fauna. Here is a detailed explanation of why Kolleru Lake is the correct answer:

1. Location:
Kolleru Lake is situated in the state of Andhra Pradesh in southeastern India. It lies between the deltas of the Krishna and Godavari rivers. The lake spreads across the districts of Krishna and West Godavari.

2. Size and Importance:
Kolleru Lake covers an area of about 245 square kilometers, making it one of the largest shallow freshwater lakes in India. It is a significant wetland ecosystem and has been recognized as a Ramsar site, which is an international designation for important wetlands. The lake provides habitat for numerous resident and migratory bird species, making it a popular destination for birdwatchers.

3. Krishna and Godavari Delta:
The Krishna and Godavari rivers are two major rivers in southern India. Both rivers have extensive delta regions where they meet the Bay of Bengal. The Krishna delta is located to the south of Kolleru Lake, while the Godavari delta is situated to the north. Kolleru Lake serves as a link between these two delta regions.

4. Ecological Significance:
The location of Kolleru Lake between the Krishna and Godavari delta regions contributes to its ecological significance. The lake acts as a vital buffer zone, helping to regulate water flow and prevent flooding in the deltas during monsoon seasons. It also serves as a breeding ground for several fish species, supporting the local fishing industry.

5. Threats and Conservation:
Kolleru Lake faces various threats such as pollution, encroachment, and unsustainable fishing practices. These factors have led to the degradation of the lake's ecosystem. To address these issues, conservation measures have been implemented, including the establishment of a Kolleru Wildlife Sanctuary to protect the lake and its biodiversity.

In conclusion, Kolleru Lake is located between the Krishna and Godavari delta regions in Andhra Pradesh, India. Its strategic location, size, and ecological significance make it an important freshwater ecosystem and a habitat for diverse flora and fauna.