Answer:
The correct answer would be "The percentage of dark brown sea lions will increase, and the percentage of light brown sea lions will decrease".
Natural selection refers to the natural phenomenon by which organisms which are better adapted to the changing environment tend to survive and reproduce more as compared to the organisms which are less adapted.
As aquatic environment make dark brown sea lions more reproductively successful thus, the offspring of dark brown sea lions would have better chances to reach the reproductive age.
Hence, with the percentage of dark brown sea lions would increase and that of light brown sea lions would decrease.