Which one of the following is not a part of Indian railway lines ?

Broad Gauge Narrow Gauge Nano Gauge Meter Gauge

Nano Gauge

On the basis of the width of track of the Indian Railways, three categories have been made: a. Broad gauge: The distance between rails in broad gauge is 1.676 metre. The total length of broad gauge lines was 60510 km in March 2016. b. Metre gauge: The distance between rails is one metre. Its total length was 3880 km in March 2016. c. Narrow gauge: The distance between the rails in this case is 0.762 metre or 0.610 metre. The total length of narrow guage was 2297 km in March 2016. It is generally confined to hilly areas.