Amphibians are vertebrates that typically live both in water and on land during different life stages. They include animals like frogs, toads, salamanders, and caecilians. While frogs (option D) are indeed amphibians, the broader category 'Amphibians' is the correct answer as it encompasses all such creatures. Cats (option B) are mammals and grasshoppers (option C) are insects - neither are vertebrates.