Introduction:
Indian Railways is one of the largest railway networks in the world, serving millions of passengers every day. Over the years, it has introduced various modern amenities to enhance the travel experience for passengers. One such amenity is internet service on trains, which has become increasingly popular in recent times. The correct answer to the question of when Indian Railways started internet service on trains is option 'D' - 1st May, 2003.

Explanation:
Indian Railways recognized the growing need for internet connectivity on trains to cater to the demands of tech-savvy passengers. Therefore, it took proactive steps to introduce internet service on trains. The following points explain the process and timeline of this development.

Planning and Implementation:
1. Recognizing the importance of internet connectivity, Indian Railways began planning the provision of internet services on trains in the early 2000s.
2. To implement this ambitious project, Indian Railways collaborated with various technology partners and service providers.
3. Extensive research and development were conducted to identify the most suitable technologies and infrastructure required for seamless internet connectivity on moving trains.

Launch of Internet Service:
1. After careful planning and execution, Indian Railways officially launched the internet service on trains on 1st May, 2003.
2. This marked a significant milestone in the history of Indian Railways as it became one of the first railway networks in the world to provide internet access to passengers on moving trains.

Benefits for Passengers:
1. The introduction of internet service on trains brought numerous benefits for passengers, enhancing their travel experience.
2. Passengers could now access the internet, browse websites, check emails, and use various online applications during their train journeys.
3. This not only helped passengers stay connected with the outside world but also provided entertainment and productivity options.
4. Business travelers, in particular, benefited from this service as they could continue working while traveling.

Expansion and Upgradation:
1. After the initial launch, Indian Railways continued to expand and upgrade its internet service on trains.
2. The network coverage and internet speed were improved to provide a seamless browsing experience for passengers.
3. Over the years, the service was extended to more train routes and coaches, making it accessible to a larger number of passengers.

Conclusion:
Indian Railways started internet service on trains on 1st May, 2003. This initiative has transformed the travel experience for passengers, allowing them to stay connected and productive during their train journeys. Indian Railways continues to improve and expand its internet service, keeping up with the evolving technological needs of passengers.