1. first
基數(shù)詞one對應(yīng)的序數(shù)詞為特殊變化,具體為first。
2. second
基數(shù)詞two對應(yīng)的序數(shù)詞為特殊變化,故本題答案為:second
3. third
基數(shù)詞three的序數(shù)詞為特殊變化,故本題答案為:third。
4. fifth
基數(shù)詞five,需變ve為f,在詞尾+th變?yōu)橄鄳?yīng)序數(shù)詞,故本題答案為:fifth.
5. ninth
基數(shù)詞nine轉(zhuǎn)換為序數(shù)詞時,需去e,在詞尾+th,故本題答案為:ninth.
6. twelfth
基數(shù)詞twelve需變f為ve在詞尾+th變序數(shù)詞,故本題答案為:twelfth.
7. twentieth
基數(shù)詞twenty需變y為i,在詞尾+eth,變序數(shù)詞,故本題答案為:twentieth.
8. twenty-first
基數(shù)詞twenty-one 變序數(shù)詞時只需變個位,故本題答案為:twenty-first.