Answer:
The correct answer is - genetic drift takes place due to disaster in favor of a green wing patch.
Step-by-step explanation:
In this given scenario there is disaster happened that wiped out 50% of a population of birds in which half had green wings and the rest half had blue wing birds before the catastrophe.
Due to this sudden catastrophe, the genetic drift occurred and also reduced the population to half and the ratio of both types of birds changed and favored the green wings as they are better adapted for the new conditions.