Answer:
The correcta answer is opcion B). "decreased variation in the shades of red because no form of the trait is advantageous".
Step-by-step explanation:
If females choose males for other traits than the red color of feathers, it is probably that the feathers would decrease the variation in the shades of red because no form of the trait is advantageous.
On the one hand, females do not choose males for this characteristic anymore, which means that this color is not advantaging for mating. On the competition with other males, they will have to develop the other trait that makes them look better genetically.
On the other hand, these bright colors make males very visible to predators, a pressure that will make the turn to less bright visible colors for better hiding and fewer chances to get caught.