Answer:
The correct answer would be natural selection.
Natural selection favors the survival and reproduction of the organisms which are better adapted to the environment.
It gradually changes the allele frequency or heritable characters of a population over the generations.
Similarly, during malaria outbreak organisms which are better adapted or resistant against the disease will survive and reproduce successfully. It will increase the frequency of allele associated with resistance or adaptation against malaria.
For example, the carriers of the sickle cell anemia show protective advantages against malaria.
The correct answer is option D, Natural selection.
The survivors within a population attacked by malarial mosquito are the individuals which have high rate of survival and reproductive rates as compared to others. The genetic qualities of these individuals have proved to be beneficial in their survival and thus their future generations consists of individuals which are able to survive in the harsh environmental conditions. This mechanism of survival of the fittest is known as natural selection.
