The correct answer is (a) Kanpur Nagar.
Kanpur Nagar is a city in the Indian state of Uttar Pradesh. It is the 11th most populous city in India and the 2nd most populous city in Uttar Pradesh after Lucknow. The city has a population of over 3.1 million people.
The density of population in Kanpur Nagar is 24,745 people per square kilometer. This is the highest density of population among all the cities in Uttar Pradesh.
The other options are incorrect because they have a lower density of population than Kanpur Nagar.
(b) Lucknow has a population of over 2.8 million people and a density of population of 19,275 people per square kilometer.
(c) Moradabad has a population of over 1.5 million people and a density of population of 11,150 people per square kilometer.
(d) Ghaziabad has a population of over 1.7 million people and a density of population of 14,200 people per square kilometer.