Three human skeletons in a single grave were recovered at

The correct answer is B, Damdama. The question asks about a grave holding three human skeletons, and Damdama in Sultanpur district of Uttar Pradesh is the site cited for this multiple-burial find in the Ganga-Gomti region's prehistoric record.

The concept here is prehistoric burial practice in the Gangetic plain. Mesolithic and Neolithic burials in this region often show grave goods, animal remains and, occasionally, multiple interments, and these clues help archaeologists infer social organisation and beliefs about death. This ties to the Ancient History section of the syllabus and to Mains questions on how early societies transitioned from hunting-gathering to settled life.

• Sarai Nahar Rai and Mahadaha are Mesolithic sites in the Pratapgarh-Prayagraj belt, known for numerous burials, which makes them tempting distractors. The question's specific feature, three skeletons in one grave, is the detail to match rather than the general number of burials.
• Langhnaj is in Mehsana district of Gujarat, not Uttar Pradesh. It is a Mesolithic site with human remains, so it is a geographic and chronological trap.

Trap: aspirants pick Mahadaha or Sarai Nahar Rai simply because they are the best-known UP Mesolithic burial sites. Match the exact feature in the question to the site, not just the region or period.