2. Man – men 2.男人
3. Datum – data 3.数据
4. Criterion – criteria 4.标准
5. Medium – media 5.媒质
6. Foot –feet 6.脚，英尺
7. Tooth – teeth 7.牙齿
8. Mouse – mice 8.老鼠
9. Sheep – sheep 9.羊
10. Crisis – crises 10.危机
11. Stimulus – stimuli 11.刺激
12. Thief – thieves 12.贼，小偷
13. Wolf – wolves 13.狼
14. Leaf – leaves 14.叶子
15. Person – people 15.人
16. Life – lives 16.生命
17. Goose – geese 17.鹅
18. Thesis - theses 18.主题
19. Potato – potatoes 19.土豆
20. Cactus – cacti 20.仙人掌