The correct answer is (a) Kanpur, Lucknow, Varanasi and Agra.
Kanpur is the largest city in Uttar Pradesh, India, with a population of 3.1 million in 2001. It is the 11th most populous city in India. Kanpur is a major industrial city, and is known for its leather and textile industries.
Lucknow is the capital of Uttar Pradesh, India, with a population of 2.8 million in 2001. It is the 12th most populous city in India. Lucknow is a major cultural and educational center, and is home to the University of Lucknow.
Varanasi is a city in Uttar Pradesh, India, with a population of 1.2 million in 2001. It is the 13th most populous city in India. Varanasi is a major Hindu pilgrimage site, and is known for its ghats (riverside steps).
Agra is a city in Uttar Pradesh, India, with a population of 1.1 million in 2001. It is the 14th most populous city in India. Agra is home to the Taj Mahal, one of the Seven Wonders of the World.
In 2001, the population of Kanpur was 3.1 million, the population of Lucknow was 2.8 million, the population of Varanasi was 1.2 million, and the population of Agra was 1.1 million. Therefore, the correct sequence of the following Million Cities of U.P. in terms of their population (2001) is (a) Kanpur, Lucknow, Varanasi and Agra.