The correct answer is option 3, which states that the position of Indian Railways network in the world is fourth. This means that the Indian Railways network is the fourth largest railway network in the world.

To better understand this, let`s briefly look at the other options:

- Option 1 states that Indian Railways is the second largest network, which is incorrect.

- Option 2 states that Indian Railways is the third largest network, which is also incorrect.

- Option 4 states that Indian Railways is the fifth largest network, which is not true.

Therefore, the correct answer is option 3, stating that Indian Railways is the fourth largest railway network in the world.