The correct answer is A. 15 kmph.
When communication is not available between the gateman and the station master, the loco pilot must reduce the speed of the train to 15 kmph. This is to ensure the safety of the train and the people at the level crossing.
Option B is incorrect because the speed limit is 15 kmph, not 10 kmph.
Option C is incorrect because the speed limit is 15 kmph, not 8 kmph.
Option D is incorrect because the speed limit is 15 kmph, not normal speed.