In a few generations, this population of beetles changed. A group of bugs includes 13 black bugs and 4 green bugs. After a few generations, there are 13 green bugs and 4 black bugs.

Which is the most likely explanation for the change?
The beetle population moved to a greener habitat.
A natural disaster almost caused the extinction of the population.
The beetle population’s food sources decreased dramatically.
A mutation resulted in a new color of insect.