C. Since they have to gain that skill.
Answer:
Mutations are changes to an organism's DNA and are an important driver of diversity in populations. Species evolve because of the accumulation of mutations that occur over time. ... This mutation has introduce a new allele into the population that increases genetic variation and may be passed on to the next generation.
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It is much darker 1000 meters deep and photosynthesis most likely can't occur, the fishes there also have different abilities than the ones higher up in order to survive, also it is probably a harder to swim because of the increased pressure