The correct answer is: a) Godavari.
The Nagarjuna Sagar Dam is a major multipurpose project on the Godavari River in the Indian state of Andhra Pradesh. It is the second largest dam in India, after the Bhakra Dam. The dam was constructed between 1955 and 1969 and is named after the 16th-century Hindu saint Nagarjuna.
The dam has a number of purposes, including irrigation, flood control, power generation, and water supply. It is also a major tourist attraction.
The Godavari River is the second longest river in India, after the Ganges. It flows through the states of Maharashtra, Telangana, Andhra Pradesh, Karnataka, and Chhattisgarh. The river is a major source of water for irrigation, drinking water, and hydroelectric power.
The other options are incorrect because they are not rivers on which the Nagarjuna Sagar Dam is located. The Krishna River is located in the states of Andhra Pradesh, Telangana, Karnataka, and Maharashtra. The Tungabhadra River is located in the states of Karnataka and Andhra Pradesh. The Pennar River is located in the states of Andhra Pradesh and Tamil Nadu.