A. One of the largest networks in the world - Indian Railways (III):
- Indian Railways is one of the largest and most extensive railway networks in the world. It plays a pivotal role in India's transportation infrastructure, connecting various regions and cities across the country.
 

B. Cheapest means of transport - Water Transport (IV):
- Water transport is often considered one of the most cost-effective modes of transportation for moving bulk goods and cargo over long distances.
 

C. Fastest means of movement - Air Transport (I):
- Air transport, which includes passenger and cargo airlines, is renowned for its speed and efficiency in moving people and goods over long distances.
 

D. Connects State capitals - National Highway (II):
- National Highways are an integral part of a country's road network and are known for connecting state capitals to one another.
 

So, the correct answer is 1. A-III, B-IV, C-I, D-II.