Illuminated A marker of semi-automatic signal means ________. A. Working as automatic signal B. Semi signal C. Outer signal D. None of these

The correct answer is: A. Working as automatic signal.

A semi-automatic signal is a type of railway signal that is controlled by a human operator, but which can be automatically operated in certain situations. When an illuminated A marker is displayed, it means that the signal is working as an automatic signal. This means that the signal will change to green automatically when it is safe for trains to proceed.

The other options are incorrect. Option B, “Semi signal”, is not a valid option. Option C, “Outer signal”, is a type of railway signal that is located outside of the main line. Option D, “None of these”, is also not a valid option.