The correct answer is option 'B' (Krishna).

Explanation:
Nagarjuna Sagar Dam is one of the largest masonry dams in the world. It is located on the Krishna River in the Indian state of Telangana. The dam is a multipurpose project that serves various purposes such as irrigation, hydroelectric power generation, and flood control.

The Krishna River:
The Krishna River is one of the longest rivers in India with a total length of approximately 1,300 kilometers. It originates in the Western Ghats near Mahabaleshwar in Maharashtra and flows through the states of Maharashtra, Karnataka, Telangana, and Andhra Pradesh before emptying into the Bay of Bengal.

Harnessing the Krishna River:
The Nagarjuna Sagar Dam project was constructed on the Krishna River at the border of Telangana and Andhra Pradesh. It was completed in 1967 and was a joint venture between the two states.

Irrigation:
One of the main objectives of the Nagarjuna Sagar Dam project is to provide irrigation water to the surrounding areas. The dam has a huge reservoir with a capacity of over 11,000 million cubic meters, which allows for the storage and regulated release of water for irrigation purposes. The water from the Krishna River is diverted into canals, which distribute the water to the agricultural fields in the region. This has significantly improved the agricultural productivity in the area.

Hydroelectric Power Generation:
The Nagarjuna Sagar Dam also harnesses the water of the Krishna River for hydroelectric power generation. The dam has a power station with a capacity of 960 megawatts, which generates electricity using the flowing water. The power generated from the dam is supplied to various cities and industries in Telangana and Andhra Pradesh.

Flood Control:
Another important function of the Nagarjuna Sagar Dam is flood control. The dam has floodgates that can be opened to release excess water during periods of heavy rainfall. This helps in preventing flooding downstream and protects the surrounding areas from the devastating effects of floods.

In conclusion, the Nagarjuna Sagar Dam project harnesses the water of the Krishna River for irrigation, hydroelectric power generation, and flood control purposes.