1. Haridwar (C) - Upstream: Haridwar is located at the northernmost point of the sequence. It is one of the major cities situated upstream along the Ganga River. Haridwar is a sacred city in Hinduism and is known for the Ganga Aarti, a daily ritual that takes place on the banks of the river. It is where the Ganga River enters the North Indian plains from the foothills of the Himalayas.

2. Kanpur (B): Kanpur is the next city in the sequence, located further downstream from Varanasi. It is an industrial city and a major urban centre in the state of Uttar Pradesh. The Ganga River flows through Kanpur and has been a centre for various industrial activities, including leather and textile production.

3. Varanasi (A): Varanasi, also known as Benares, is the next city in the sequence. It is situated downstream from Haridwar. Varanasi is one of the oldest and most sacred cities in India and is located on the banks of the Ganga River. It is known for its ghats (steps leading to the river) and is a significant religious and cultural centre.

4. Patna (D) - Downstream: Patna is the last city in the sequence and is located further downstream along the Ganga River. It is the capital of the Indian state of Bihar and is one of the largest cities in eastern India. Patna has a rich historical and cultural heritage and is a key centre for trade and commerce in the region. The Ganga River flows through the city before continuing on its journey to the Bay of Bengal.