The correct answer is option 2, Samudragupta. The Gupta dynasty was known for its support of Buddhism, and under the rule of Samudragupta, Meghaverman, the ruler of Sri Lanka, was granted permission to build a Buddhist temple at Gaya.

Option 1, Chandragupta I, is incorrect. Although Chandragupta I was an important ruler of the Gupta dynasty, there is no historical evidence to suggest that he granted permission to Meghaverman to build a Buddhist temple at Gaya.

Option 3, Chandragupta II, is also incorrect. Although Chandragupta II, also known as Chandragupta Vikramaditya, was a prominent ruler of the Gupta dynasty and known for his patronage of the arts, there is no historical evidence to suggest that he granted permission to Meghaverman for building a Buddhist temple.

Option 4, Skandagupta, is incorrect as well. Skandagupta was a later Gupta king known for his military prowess and efforts to defend the empire against foreign invasions. There is no historical evidence to suggest that he granted permission for the construction of a Buddhist temple at Gaya.