When the section is occupied, the arrow indication in the panel in Twin single line working will be A. White B. Red C. No light D. None of these

The correct answer is B. Red.

When the section is occupied, the arrow indication in the panel in Twin single line working will be red. This is to indicate to the driver that the section is occupied and that they should not proceed.

The other options are incorrect. Option A is incorrect because white is the color used to indicate that the section is clear. Option C is incorrect because no light would indicate that the section is not occupied. Option D is incorrect because there is no other option that is correct.