In Both Field and Lab Studies of Guppies, You Observe

In both field and lab studies of guppies, you observe a rapid evolutionary change in the physiological traits that help the animals avoid predation. This observation illustrates which main point?

A) Allele frequency is maintained in all conditions.
B) Natural selection is an ongoing process.
C) Dominant genes will always increase survival rates.
D) Evolutionary change is facilitated by natural selection.