The sentence should instead be this: Which moves more swiftly through the water, a shark or a crocodile. Although this is starting to slip from common usage.
The correct answer should be Find the meaning of the word "terminating" in an online dictionary.
Finding it in an online dictionary would be rather easy and quick, while it would also be the most correct since the world does not have a polysemic meaning in this context. Context can be tricky while finding antonyms would not be that useful.
