Answer: D natural selection
Step-by-step explanation:
Natural selection can be define as the phenomena of differential survival and reproduction of organisms who possess better phenotypic traits. According to the given situation, the two allele colors of the beetles like brown and green. The population would likely to have gene pool of green beetles in future. This is due to the fact that they have green color as a phenotypic trait, which prevent their detection by the predators in grass. These bettles will survive and reproduce.