The correct answer is: a) Godavari and Krishna.
The coastal plains of Andhra Pradesh are formed by the deltas of the Godavari and Krishna rivers. The Godavari River is the second-longest river in India, and the Krishna River is the third-longest. Both rivers flow from the Western Ghats to the Bay of Bengal. The deltas of these rivers are very fertile and are home to a large population.
The Godavari River delta is located in the eastern part of Andhra Pradesh. It is the largest delta in India, and it is home to a number of important cities, including Kakinada, Rajahmundry, and Eluru. The delta is a major agricultural region, and it is also home to a number of industries.
The Krishna River delta is located in the western part of Andhra Pradesh. It is the second-largest delta in India, and it is home to a number of important cities, including Vijayawada, Guntur, and Nalgonda. The delta is a major agricultural region, and it is also home to a number of industries.
The other options are incorrect because they do not include both the Godavari and Krishna rivers. The Pennar River is a tributary of the Krishna River, and the Mahanadi River is located in the state of Odisha.