According to Census 2011, what is the correct descending order of population size for the major Indian urban agglomerations Delhi, Mumbai, Kolkata and Chennai?

Introduction / Context:
Urban agglomerations are continuous urban spreads that include a city and its adjoining urban areas. Census 2011 is a crucial reference point for questions on India's population geography. Competitive examinations often ask about the ranking of India's largest cities or urban agglomerations by population. This question checks whether you know the relative sizes of Mumbai, Delhi, Kolkata and Chennai as per the 2011 Census, which is still widely used as the latest official census data for population comparisons in many exams.

Given Data / Assumptions:
- Four major urban agglomerations are involved: Mumbai, Delhi, Kolkata and Chennai. - The reference year for population is Census 2011. - We must arrange the cities in descending order, from largest population to smaller. - Only one of the given sequences correctly matches the 2011 Census urban agglomeration rankings.

Concept / Approach:
As per Census 2011, the largest urban agglomeration by population in India was Mumbai, followed very closely by Delhi. Kolkata had the third largest urban agglomeration, and Chennai ranked below these three. The key concept is to recall that Mumbai remained marginally ahead of Delhi in 2011, even though Delhi's growth was rapid. Therefore, any sequence where Delhi appears before Mumbai in a descending list is automatically incorrect. Similarly, Kolkata cannot appear above either Mumbai or Delhi, and Chennai cannot be ranked above Kolkata in this specific census ranking.

Step-by-Step Solution:
Step 1: Recall that Mumbai had the highest urban agglomeration population in 2011, so it must come first in any descending order. Step 2: Delhi was the second largest urban agglomeration, so it must come immediately after Mumbai. Step 3: Kolkata was ranked third, so it follows Delhi in the sequence. Step 4: Chennai, being smaller than Kolkata in urban agglomeration population, must come last among the four. Step 5: The correct descending order is therefore Mumbai – Delhi – Kolkata – Chennai, which matches option "Mumbai – Delhi – Kolkata – Chennai".

Verification / Alternative check:
A quick check is to remember headline facts: Mumbai and Delhi are always cited as India's top two megacities, with figures above 16 million in their urban agglomerations in 2011. Kolkata is traditionally the third major metropolis of eastern India, and Chennai is an important southern metropolis but with a slightly smaller urban agglomeration population. Whenever you see an option where Delhi appears before Mumbai or Kolkata appears ahead of Delhi, that option conflicts with census based rankings and can be eliminated.

Why Other Options Are Wrong:
Delhi – Mumbai – Kolkata – Chennai is wrong because Delhi cannot precede Mumbai in descending order when Mumbai had the larger agglomeration population in 2011.
Mumbai – Kolkata – Delhi – Chennai is wrong because Kolkata did not outrank Delhi; Delhi's agglomeration was larger than Kolkata's.
Kolkata – Chennai – Mumbai – Delhi is wrong because it incorrectly places Kolkata and Chennai before Mumbai and Delhi, contradicting both common knowledge and census data.

Common Pitfalls:
Students sometimes confuse city proper population with urban agglomeration population, or they recall newer projections where Delhi may overtake Mumbai and apply these to older census questions. Another trap is relying on regional prominence rather than actual numerical rankings, which leads some candidates to think Kolkata might be second largest due to its historic importance. Always pay attention to the reference year mentioned in the question and remember that for Census 2011 the order remains Mumbai first, Delhi second, Kolkata third and Chennai fourth.

Final Answer:
In Census 2011 the correct descending order of population size for these urban agglomerations is Mumbai – Delhi – Kolkata – Chennai.