The correct answer is “sharp-fanged cat”
“Sharp-fanged cat” is a compound word. Compound words can be written on a closed form when the words are written together, with a hyphenated form where words are joined by a hyphen and with an open form where the words are open and create a new meaning when read together.
In this case, two words “sharp” and “fanged” are joined together by a hyphen. This creates a new word with a new meaning, a cat that has the shape of a fange.