The correct answer is Option 1- Chandragupta II

The Iron Pillar of Mehrauli was built by Chandragupta II.

Chandragupta II (reigned c. 380–c. 415 CE) was the fourth emperor of the Gupta Empire in ancient India. He was a brilliant military strategist and a skilled diplomat, and he quickly expanded the empire to include much of northern India.

Chandragupta II was also a great patron of the arts and learning. He established schools and libraries, and he supported scholars and artists. He was himself a poet and a musician, and he encouraged the development of literature, music, and sculpture during his reign.

The Iron Pillar of Mehrauli is a 7.21-meter-high iron pillar that is located in the Qutub complex in Mehrauli, Delhi, India. It is believed to have been erected by Chandragupta II in the early 5th century CE. The pillar is notable for its resistance to corrosion, and it is considered to be one of the finest examples of ancient Indian ironworking.