Explanation:

- Hooghly River:

- This is the correct option.

- India's first underwater metro tunnel is under the Hooghly River.

- This tunnel is part of the Kolkata Metro East-West Corridor project.

- Yamuna River:

- An important river flowing through northern India, especially Delhi.

- No known metro tunnel projects under this river.

- Ganga River:

- One of the most significant rivers in India.

- However, no underwater metro tunnel has been constructed here.

- Gomti River:

- Flows through Uttar Pradesh, notably Lucknow.

- No underwater metro tunnel project is associated with this river.

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