The correct answer to the question is option 2, the Mahabodhi Temple in Bodh Gaya. In the year 2002, UNESCO declared the Mahabodhi Temple as a World Heritage Site.

Option 1, the Mahadeva Temple in Khajuraho, was not declared a World Heritage Site by UNESCO in 2002. It may still be a significant temple, but it did not receive this specific recognition in that year.

Option 3, the Lingaraja Temple in Bhubaneswar, was also not declared a World Heritage Site by UNESCO in 2002. Again, this temple may have its own significance, but it did not receive the specific recognition mentioned in the question.

Option 4, the Hoysaleswara Temple in Halebid, was not declared a World Heritage Site by UNESCO in 2002. While it may have its own historical and cultural value, it did not receive the designated recognition in that particular year.

Therefore, the Mahabodhi Temple in Bodh Gaya was the only temple in the options provided that was declared a World Heritage Site by UNESCO in 2002.