Which is the largest multipurpose river valley project in India?
A. Bhakra Nangal
B. Damodar Valley
C. Nagarjunasagar
D. Tungabhadra

Hint:A gravity dam in Bilaspur on the Sutlej River, Himachal Pradesh. The world's highest straight-gravity dam (225,5 m high) on the Sutlej River.

Complete answer:
The Bhakra Nangal Project is the largest multi-purpose river valley project in India and the highest straight gravity dam on the Sutlej River in the world (225.5 m tall).
In Bilaspur, Himachal Pradesh in northern India, Bhakra Dam is a concrete gravity dam on the Sutlej river.
The dam forms the reservoir of Gobind Sagar. The dam's length measured from the road above is 518.25 m and its width is 9.1 m. The Gobind Sagar reservoir stores up to 9.34 billion cubic metres of water. An area of 168.35 km2 is spread over the 90 km long reservoir formed by the Bhakra Dam.

Now lets see the options :-
Bhakra nangal- Bhakra Nangal Project is India's largest multi-purpose river valley project and the world's highest straight gravity dam (225.5 m high) on the Sutlej River. Thus this right option
Damodar valley:- The Damodar Valley Project is Eastern India's first major multipurpose river valley creation project but it is not largest thus this is the wrong option.
Nagarjunasagar:- Nagarjuna Sagar Dam, 590 feet (180 m) high from its lowest base, is a masonry dam across the Krishna River at Nagarjuna Sagar. Thus, this is also the wrong choice.
Tungabhadra- From the deepest base, Tungabhadra is 49.50 m (162 ft) long thus this is the wrong option too.
Thus option A is the right choice.

Note:The Bhakra-Nangal Dam is the second highest dam in Asia after the 207.26 metre high Tehri Dam.
Back in 2013, it was the only dam in Asia to have the capacity to generate 1500 MW of electricity.