Correct Option (B):
The Sea cow (also known as dugong or manatee) and Sea lion are both classified as mammals. Mammalian characteristics include giving birth to live young and nursing them with milk, which both these animals exhibit. Sea cows are herbivorous marine mammals, while Sea lions are carnivorous marine mammals belonging to the eared seal family.
In contrast, the Seahorse is a type of fish, not a mammal. It possesses gills for respiration, fins for movement, and a body covered in bony plates, lacking mammary glands for milk production.
Incorrect Options:
- Option (A) is incorrect because while the Sea cow is a mammal, the Sea lion is also a mammal and is omitted from this option.
- Option (C) is incorrect because the Seahorse is a fish, not a mammal.
- Option (D) is incorrect because it includes the Seahorse, which is a fish and not a mammal.