The type of levelling operations carried out for laying a railway track are
1. Longitudinal levelling (L. S.)
2. Fly levelling
3. Barometric levelling
4. Cross-sectioning
Select the correct answer using the codes given below:1
1, 2 and 3 only
2
1, 3 and 4 only
3
2, 3 and 4 only
4
1, 2 and 4 only