Identify the highest dam in India from the given options (by structural height).

Introduction / Context:
India has several large dams serving irrigation, hydropower, and flood control. Among widely cited structures, Bhakra (Bhakra–Nangal) is notable for its great height, while Hirakud is famous for its enormous length and reservoir capacity.

Given Data / Assumptions:

• Compare structural heights among the listed dams.
• Standard indicative heights: Bhakra ~226 m; Idukki ~169 m; Nagarjuna Sagar ~124 m; Hirakud ~60 m (approximate structural height; it is the longest).
• Minor variations by source do not change the ranking among these options.

Concept / Approach:

Determine which dam has the maximum height from riverbed/foundation to crest among the given choices. Despite Hirakud’s length, its height is lower than Bhakra’s. Idukki and Nagarjuna Sagar are also lower than Bhakra by several tens of metres.

Step-by-Step Solution:

Verification / Alternative check (if short method exists):

Cross-reference standard engineering handbooks or government sources; rankings remain consistent.

Why Other Options Are Wrong:

Hirakud’s fame is for length, not height; Idukki and Nagarjuna Sagar are tall but not as tall as Bhakra among the provided choices.

Common Pitfalls (misconceptions, mistakes):

Confusing “largest” (by volume/length/capacity) with “highest”; overlooking that Tehri (taller) is not among the options.

Final Answer:

Bhakra dam