The boring of India first underwater rail tunnel has been completed under which river?

Introduction / Context:
Underwater rail tunnels are major engineering achievements that allow trains to pass beneath rivers or seas. India first underwater rail tunnel was constructed as part of a metro rail project, and its boring work was a significant milestone. This question checks knowledge of the specific river under which this first underwater tunnel was completed.

Given Data / Assumptions:

The structure is India first underwater rail tunnel.
The question asks under which river this tunnel was bored.
Four important Indian rivers are listed as options.
The focus is on the boring stage being completed.

Concept / Approach:
The concept involves basic Indian geography and awareness of infrastructure projects. The first underwater metro tunnel in India was built under the Hooghly River as part of the Kolkata Metro expansion. Remembering the connection between Kolkata Metro and the Hooghly River leads to the correct answer.

Step-by-Step Solution:
Step 1: Recall which city is associated with India first underwater metro tunnel, namely Kolkata. Step 2: Identify the main river flowing near Kolkata, which is the Hooghly River. Step 3: Match this river with the options and select Hooghly River as the correct answer.

Verification / Alternative check:
Infrastructure project reports, government announcements, and news articles all state that India first underwater rail tunnel was constructed under the Hooghly River as part of Kolkata Metro. Checking several such sources confirms that option A is correct and the other rivers are not associated with this particular tunnel.

Why Other Options Are Wrong:
Kaveri River flows through southern India and is not the site of this specific underwater rail tunnel, so option B is incorrect.
Godavari River is a major river but has not been linked with India first underwater rail tunnel, making option C wrong.
Krishna River is another large river in southern India, yet no underwater rail tunnel boring was first completed under it, so option D is also incorrect.

Common Pitfalls:
Students may confuse projects like river bridges, tunnels, and metro works across different regions. Another pitfall is focusing on famous rivers like the Ganga and ignoring local branches such as the Hooghly. By associating Kolkata Metro with the Hooghly River, candidates can confidently remember the correct answer.

Final Answer:
The boring of India first underwater rail tunnel was completed under the Hooghly River.