The Five states with largest route kilometers are as follows:

Uttar Pradesh : 8726.

Rajasthan : 5780.

Maharashtra: 5602.

Andhra Pradesh: 5241.

Gujarat : 4999.

The correct answer is option 'B', Uttar Pradesh. Uttar Pradesh has the largest railway network in India. Let's delve into the details to understand why.

1. Railway Network:
- Uttar Pradesh has an extensive railway network, covering a large portion of the state.
- It has a vast network of railway lines that connect various cities, towns, and villages within the state as well as provide connectivity to other states.

2. Geographical Advantage:
- Uttar Pradesh is the most populous state in India and is geographically located in the central-northern part of the country.
- Due to its large population and strategic location, it requires an extensive railway network to cater to the transportation needs of its people.

3. Major Railway Zones:
- Uttar Pradesh is divided into five major railway zones, which are Northern Railway, North Eastern Railway, North Central Railway, Eastern Railway, and North Western Railway.
- These zones collectively manage the vast railway infrastructure in the state and ensure smooth operations.

4. Important Railway Junctions:
- Uttar Pradesh is home to several important railway junctions, which act as major hubs for train operations.
- Some of the prominent junctions in the state include Kanpur Central, Lucknow Junction, Varanasi Junction, Allahabad Junction, and Gorakhpur Junction.
- These junctions not only serve the state but also act as crucial transit points for trains passing through Uttar Pradesh.

5. Historical Significance:
- Uttar Pradesh has a rich historical and cultural heritage. It is home to several UNESCO World Heritage Sites, such as the Taj Mahal, Agra Fort, and Fatehpur Sikri.
- The presence of these iconic landmarks attracts a significant number of tourists, both domestic and international.
- To cater to the transportation needs of tourists, Uttar Pradesh requires a well-developed railway network.

Conclusion:
Considering the extensive railway network, geographical advantage, major railway zones, important junctions, and historical significance, it is evident that Uttar Pradesh has the largest railway network in India. The state's railway infrastructure plays a crucial role in connecting various regions, facilitating the movement of people and goods, and promoting tourism.