The correct answer is Ludhiana.
Ludhiana is the most populous district in Punjab, India. It has a population of over 3.5 million people. The district is located in the northwestern part of the state and is known for its industrial development. Ludhiana is also home to a number of educational institutions, including Punjab University.
Amritsar is the second most populous district in Punjab. It has a population of over 2.5 million people. The district is located in the eastern part of the state and is home to the Golden Temple, one of the most important Sikh shrines. Amritsar is also a major tourist destination.
Jalandhar is the third most populous district in Punjab. It has a population of over 2 million people. The district is located in the northwestern part of the state and is known for its educational institutions, including Guru Nanak Dev University. Jalandhar is also a major industrial center.
Patiala is the fourth most populous district in Punjab. It has a population of over 1.5 million people. The district is located in the central part of the state and is the former capital of Punjab. Patiala is home to a number of historical monuments, including the Sheesh Mahal and the Moti Bagh Palace.
In conclusion, Ludhiana is the most populous district in Punjab. It has a population of over 3.5 million people. The district is located in the northwestern part of the state and is known for its industrial development. Ludhiana is also home to a number of educational institutions, including Punjab University.