Imani Grew Up in a Region of Africa Where Malaria

Imani grew up in a region of Africa where malaria is prevalent. Many in her community that have lived there for generations seem to have increased resistance to the disease compared to families who have recently moved to the area. However, others moved away from Africa to areas without malaria where the gene was not needed to protect against the disease. This instance is an example of a

A) negative mutation.
B) neutral mutation.
C) positive mutation.
D) fixed-region mutation.
E) mixed mutation.