The driver shall sound the following whistle to indicate that the fouling marks is not clear A. Three long B. Short one long C. One long D. None of these

The correct answer is A. Three long whistles.

The fouling marks are the white lines on the track that indicate the boundaries of the track. The driver must sound a whistle to indicate that the fouling marks are not clear if the train is approaching the fouling marks and there is a risk of the train going off the track. The whistle must be sounded three times in quick succession.

Option B is incorrect because it is not the correct number of whistles to sound. Option C is incorrect because it is not the correct type of whistle to sound. Option D is incorrect because it is not a valid option.