In the Delhi Sultanate, the one-fifth share of war booty, mines and treasure troves claimed by the state was called:

"Khams" (meaning "one-fifth") was the tax by which the state took one-fifth of the war booty, mines and buried treasure (treasure troves), according to Islamic law.

About Khams:

• According to Islamic law (Sharia), four-fifths of the booty captured in war was to be distributed among the soldiers, and one-fifth (khams) was to go to the state (the ruler).
• The same share was to be taken from the produce of mines and from treasure found buried in the earth.
• In practice, some Sultans took a much larger share of the booty.
• Alauddin Khalji reversed the proportion, taking four-fifths of the war booty for the state and leaving only one-fifth for the soldiers.
• Firoz Shah Tughlaq, who wanted to follow the Sharia strictly, restored the original practice, taking only one-fifth for the state.

The four taxes approved by the Sharia:

• Firoz Shah Tughlaq abolished many taxes that were not approved by Islamic law, and collected only the four taxes sanctioned by it:
• A land tax on cultivators.
• "Jizya": a tax on non-Muslims, in return for protection and exemption from military service.
• "Khams": one-fifth of the war booty, mines and treasure troves.
• "Zakat": a religious tax of 2.5 percent on the wealth of Muslims, to be spent on religious and charitable purposes.
• "Ushr": a land tax (one-tenth of the produce) on land owned by Muslims, also mentioned in some lists.

Other sources of state income:

Taxes on trade (customs duties), and taxes on houses and cattle.

The meaning of the word:

"Khams" is the Arabic word for "five", and the tax was literally "the fifth".

Why not the other options?

• ✗Zakat was a religious tax on Muslims.
• ✗Jizya was a tax on non-Muslims.
• ✗Ushr was a tithe on land owned by Muslims.