Which of the following rivers of Uttar Pradesh has been declared a 'Biological Disaster due to environmental pollution?

1. A

   Yamuna

   The Yamuna in Uttar Pradesh is heavily polluted, especially downstream of Delhi, but the paper’s ‘biological disaster’ tag for this item is not Yamuna. This option is not the key.

2. B

   Gomati

   The Gomati, Lucknow’s river, has been officially discussed as a biological disaster because untreated sewage and urban waste collapsed its aquatic life. That is the stored pairing. This option is the official key.

3. C

   Sai

   The Sai is a Gomati tributary and faces pollution, but it is not the named disaster river in the key. This option is therefore wrong.

4. D

   Tamsa

   The Tamsa (Tons) of eastern UP is not the river declared as asked. This option is not the key.

Summary. Official key is (b) Gomati. Lucknow’s stretch has suffered oxygen collapse and fish kills from municipal discharge, prompting the biological-disaster language in contemporary reports used by the paper. Yamuna, Sai and Tamsa are other UP rivers with their own pollution stories. Only (b) is keyed.