The correct answer is: A. 5 kmph
ISMD stands for “In-Service Maintenance Depot”. It is a facility where trains are taken for maintenance while they are still in service. When an ISMD attached train is allowed to run through on PF line, the speed must be 5 kmph. This is because the train is carrying heavy equipment and is not as maneuverable as a regular train. Running at a higher speed could increase the risk of derailment.
Option B is incorrect because 8 kmph is too fast for a train carrying heavy equipment. Option C is incorrect because 10 kmph is also too fast for a train carrying heavy equipment. Option D is incorrect because it is not a valid option.