What title was formerly given to the fort?

A Ruby amongst the fortresses of Hind
B Diamond amongst the fortresses of Hind
C Pearl amongst the fortresses of Hind

The grandeur of the Gwalior fort impressed the ruler, Zahir ud din Muhammad Babur, who referred to the fort as the ‘pearl amongst the fortresses of Hind’.

The correct answer is Pearl amongst the fortresses of Hind.