按要求写单词。
1. activity (复数) __________________
2. sheep (单数) __________________
3. down (反义词) __________________
4. calf (复数) __________________
5. let's (原形) __________________
6. children (单数) __________________
7. play (三单) __________________
8. joey (复数) __________________
9. baby cats (同义词) __________________
10. that (复数) __________________