Which is the most likely reason for the high population density in the north eastern part of India

There is no pollution there
The gauges river is in that region
Most people want to live closer to the Himalayan mountains
The areas to conflict between hindus and Muslims

The most likely reason for the high population density in the north eastern part of India is the proximity to the Himalayan mountains. Many people are attracted to live closer to the mountains due to their scenic beauty, potential for tourism, and access to natural resources.