The correct answer is: B. Automatic stop signal+120 Meters
The LSS (Leading Locomotive Signal) is a signal that is placed in front of a locomotive to indicate the next signal. The LSS shall not be taken off unless the line is clear upto the automatic stop signal plus 120 meters. This is to ensure that the locomotive does not enter a section of track that is occupied by another train.
The other options are incorrect because they do not provide the required clearance for the locomotive. Option A (Next automatic stop signal) does not provide enough clearance, as the locomotive could enter a section of track that is occupied by another train. Option C (Automatic stop signal+180 Meters) provides too much clearance, as the locomotive would have to wait unnecessarily before proceeding. Option D (None of these) is incorrect because it does not provide any guidance on the required clearance.
In conclusion, the correct answer is: B. Automatic stop signal+120 Meters.