A group of zoologists discovered the presence of a new species of octopus in the Pacific Ocean. This case is related to the study of

Explanation

The correct answer is marine biology. This field focuses on the study of life forms in the ocean, which directly aligns with the discovery of a new species of octopus in the Pacific Ocean. Fresh water biology is incorrect because it pertains to life in inland waters, not the ocean. Molecular biology is not directly related to species discovery in the context of natural habitats. Parasitology focuses on parasites, which is not relevant to the discovery of an octopus species.