The correct option is It is constructed primarily of bronze and copper..
Explanation
The Iron Pillar at Mehrauli, Delhi, is a significant archaeological evidence of the advanced metallurgical skills possessed by Indian craftsmen during the Gupta period. Standing near the Qutub Minar, it is renowned for its composition and preservation.
Statement-wise Analysis:
- Statement It was manufactured approximately 1500 years ago. is Correct: The pillar is estimated to have been manufactured approximately 1500 to 1600 years ago, dating back to the Gupta period (circa 4th–5th century CE).
- Statement It bears an inscription mentioning a ruler named Chandra. is Correct: The pillar bears a Sanskrit inscription in Brahmi script which mentions a ruler named 'Chandra'. This ruler is historically identified with Chandragupta II (c. 375–415 CE) of the Gupta dynasty.
- Statement It is constructed primarily of bronze and copper. is Incorrect: The pillar is not made of bronze or copper. It is composed almost entirely of wrought iron (over 98% pure iron). Its survival without significant rusting for centuries is its defining characteristic.
- Statement It is known for its high resistance to corrosion. is Correct: The pillar is globally famous for its high resistance to corrosion. This rust resistance is attributed to the formation of a passive protective film (misawite) on the surface, resulting from the high phosphorus content and the specific manufacturing process used by ancient Indian metallurgists.
Key Takeaway:
The Mehrauli Pillar is a masterpiece of Gupta-era metallurgy made of wrought iron, famous for its non-rusting properties and the inscription of King Chandra (Chandragupta II).