Colour of the semaphore calling on signal is ________. A. Red B. White C. Green D. None of these

The correct answer is A. Red.

A semaphore is a device for railway signalling, consisting of a mechanical arm or arms which can be moved to indicate different aspects. The red aspect is used to indicate that the train must stop before proceeding.

The white aspect is used to indicate that the train may proceed at caution.

The green aspect is used to indicate that the train may proceed at full speed.

None of these is the correct answer because the semaphore calling on signal is red.