Step 1: Understanding the Concept:
Khetri is a town in Jhunjhunu district, Rajasthan, and it is named in Indian geography chiefly for one specific mineral resource.
Step 2: Identify the mineral.
The Khetri Copper Belt is one of India's oldest and most important sources of copper ore, mined and processed there since ancient times and developed further after independence through Hindustan Copper Limited.
Step 3: Why the other options are wrong.
Bauxite (the ore of aluminium) is mined mainly in Odisha, Jharkhand, Chhattisgarh and Gujarat, not Khetri. Iron ore's leading belts are in Odisha, Chhattisgarh, Jharkhand and Karnataka. Manganese is chiefly mined in Odisha, Madhya Pradesh, Maharashtra and Karnataka. None of these three point to Khetri.
Final Answer:
Khetri is famous for copper.\[ \boxed{\text{Copper}} \]