In the history of the Delhi Sultanate, which Sultan was the first to adopt the systematic measurement of cultivable land as the basis for assessing land revenue?

Introduction / Context:
Land revenue was the main source of income for medieval Indian states. How rulers calculated and collected this revenue tells us a lot about their administrative innovations. The Delhi Sultanate saw several experiments with revenue systems. This question asks about the first Sultan who introduced the principle of measuring cultivable land in order to fix land revenue more systematically.

Given Data / Assumptions:

• The period is the Delhi Sultanate, not the Mughal Empire.
• The focus is on systematic measurement of land for revenue assessment.
• Several well known Sultans are listed as options.

Concept / Approach:
Before scientific measurement, revenue demands were often based on rough estimates or traditional shares. Ala ud din Khalji, known for his market and revenue reforms, ordered measurement of land in certain regions to fix a standard share of produce as revenue. Later rulers such as Sher Shah and Akbar developed more elaborate systems, but Khalji action represents an early step in this direction within the Sultanate.

Step-by-Step Solution:
Step 1: Recall that Ala ud din Khalji ruled from the late thirteenth to early fourteenth century and is famous for strong administrative control. Step 2: Remember that his reforms included market regulation and strict revenue assessment based partly on measurement of land. Step 3: Note that Iltutmish and Balban came earlier and did not introduce such systematic measurement. Step 4: Ghiyas ud din Tughluq and Muhammad bin Tughluq tried other revenue experiments, but the first clear adoption of measurement principle is associated with Khalji. Step 5: Therefore, among the options, Ala ud din Khalji is the correct choice.

Verification / Alternative check:
History texts describing Ala ud din Khalji reforms highlight his attempt to bring revenue closer to half of the produce and to base demands on measured land rather than arbitrary estimates. Later revenue systems in the Mughal period drew on this idea in more systematic ways. This confirms that he was the pioneer of such measurement among the listed Sultans.

Why Other Options Are Wrong:
Option A, Ghiyas ud din Tughluq, introduced reforms but is not credited as the first to use systematic measurement for revenue. Option B, Iltutmish, helped consolidate the Sultanate but did not pioneer this method. Option D, Balban, focused mainly on strengthening the monarchy and military discipline. Option E, Muhammad bin Tughluq, experimented with various revenue ideas but came after Khalji and is not the first in this respect.

Common Pitfalls:
Some learners mistakenly attribute all revenue innovations to later rulers like Sher Shah or Akbar and forget the earlier experiments under the Delhi Sultans. Others confuse Muhammad bin Tughluq radical measures with scientific measurement. To answer correctly, remember the association between land measurement and Ala ud din Khalji within the Delhi Sultanate.

Final Answer:
The first Sultan to adopt the principle of measuring cultivable land for revenue assessment was Ala-ud-din Khalji.