Correct sentence (simple): Reindeer use their sharp, hard hooves to dig moss out from under the ice.
Why this is better (step by step):
- Subject and verb: "Reindeer use" is correct because "reindeer" is plural and matches the verb "use."
- Adjectives: "sharp" and "hard" both describe the hooves. When two adjectives describe the same noun and are equal, put a comma between them: "sharp, hard hooves."
- Word order: "dig moss out from under the ice" sounds natural. You can also say "dig out moss from under the ice." Both are correct.
- Possessive word: "their" correctly shows the hooves belong to the reindeer.
Other simple ways to say it:
- "Reindeer use their strong hooves to dig moss out from under the ice."
- "Reindeer dig moss from under the ice with their strong hooves."
Nice job—your original sentence was almost perfect. Adding the comma and choosing small word changes makes it read a bit more smoothly.