Frog is to dinosaur as a whale is to a. mouse b. fish c. bird d. snake?

Ok lets see... "Dinosaur" is a pretty vague name in terms of ecological niches, locomotion, and every other thing I could think of that would unite them into something polarized from Whales and Frogs. So the analogy has to be something about how the are related. Dinosaurs are Archosaurian Diapsid Reptiles, the ancestors of Amphibian, of which Frogs are a derived form of. But whales don't have any descendents that can be considered distinct enough from them as Dinosaurs are from frogs. Dolphins? That doesn't make any sense, Dolphins are still Whales, but Dinosaurs aren't Frogs. Maybe it is about being vague, like, Dinosaurs covered a wide range of diets, habitats, and the like but aren't particularily known for being amphibious, unless you count diving birds and penguins as "amphibious" (which I don't). So what's a group of animals that covers a broad range of forms but excludes fully marine life? ...um, uh... ...some sort of worm? I don't know this is hard. I'm probably overthinking this, but there doesn't seem to be an obvious answer. So I'm just going to guess. Fog : Dinosaur :: Whale : PlesiOSaur Thats probably wrong, but whatever.