I have always been fascinated by words whose plurals don't add the regular "S." So this week, my challenge is to identify the plural form of each of the following words. Spelling will definitely count. This activity is worth .3 each, making this worth 3 bonus points. You may need to consult a dictionary or the Internet to find the answers.1. cactus
2. crisis
3. appendix
4. ox
5. memorandum
6. series
7. nebula
8. hoof
9. motto
10. sister-in-law
