Concept:
The spatial density of railway networks across India is profoundly conditioned by physiography, population density, economic resources, and level of industrialization.
Flat alluvial plains provide the most favorable physical and socioeconomic conditions for laying down dense railway tracks.
Step 1: Contrast as Described in the Passage:
The passage points out where railways are sparse:
"The railway network is relatively less dense in the hill states, north eastern states, central parts of India and Rajasthan."
Rugged relief, steep gradients, dense forest cover, and dispersed settlements create severe engineering and economic barriers in the Himalayan hill states and North Eastern region.
Step 2: Why the Ganga Plains Have a Dense Network:
In sharp contrast, the northern alluvial Ganga plains feature:
1. Vast, uniform, level plain topography requiring minimal grading, tunnels, or deep cuts.
2. Extremely high agricultural productivity and rural population density.
3. A large concentration of major commercial towns and industrial hubs.
Consequently, the Ganga plains support one of the densest railway networks in the world.
Final Answer:
Therefore, the Ganga plains have a dense railway network.