Option 1: Vidyaranya, also known as Madhava Vidyaranya, was a 14th-century philosopher and spiritual leader. He was not involved in the construction of the monumental `Raya-gopurams` in front of the temples mentioned in the question.

Option 2: Krishnadevaraya was indeed responsible for the construction of the monumental `Raya-gopurams` in front of the temples at Hampi, Tiruv-annamalai Chidambaram, Srirangam, Tiru-pati, etc. Krishnadevaraya was the ruler of the Vijayanagara Empire from 1509 to 1529 and was known for his patronage of art, architecture, and literature.

Option 3: Harihara was one of the founders of the Vijayanagara Empire but he did not construct the `Raya-gopurams`.

Option 4: Rajaraja, also known as Rajaraja the Great, was a ruler of the Chola Empire in the 10th century. However, he ruled much before the construction of the `Raya-gopurams` and was not involved in their construction.

The correct answer is option 2, Krishnade