The length of long welded rail under Indian conditions should be about A. 1 km B. 2 km C. 0.50 km D. None of these

1 km
2 km
0.50 km
None of these

The correct answer is A. 1 km.

Long welded rails are used in railways to reduce the number of joints in the track. This makes the track smoother and more stable, which can improve safety and reduce wear and tear on the track. The length of long welded rails varies depending on the country and the type of railway. In India, the length of long welded rails is typically 1 km.

Option B is incorrect because 2 km is too long for a long welded rail. Option C is incorrect because 0.50 km is too short for a long welded rail. Option D is incorrect because it is not a valid option.