The correct answer is option 4, which is none. This means that the length of Indian rails has not increased in the last fifty years.
Options 1, 2, and 3 suggest a percentage increase in the length of Indian rails. Option 1 suggests an increase of 16.6%, option 2 suggests an increase of 24.8%, and option 3 suggests an increase of 30.2%. However, these options are not correct according to the given answer.
Therefore, it can be concluded that the length of Indian rails has remained the same over the last fifty years. It is important to note that although the provided answer is correct, it may be beneficial to further research the topic to confirm the accuracy of the given information.