Final answer:
A positive correction factor is added to the applicable minima when separating a beacon target from a primary target on a radar display to account for downward movements, which are conventionally assigned a negative sign.
Step-by-step explanation:
When using a radar target display with a previously specified beacon target displacement to separate a beacon target from a primary target, adjacent airspace, obstructions, or terrain, you should add a positive correction factor to the applicable minima. This is consistent with the convention in physics and engineering where a downward movement is assigned a negative sign, which is option b.
Therefore, when adjusting minimum separation distances to ensure safe navigation and to account for potential inaccuracies in radar displays, a positive correction factor is applied to counteract these negative displacements. This method ensures aircraft are not at risk due to being closer than radar readings suggest, as would occur with uncorrected negative displacements.