1.I finished the work first.
2.you go first.
3.This is the second time that you called me.
4.Joe is my second son.
5.The third is what I really want.
6.Tom is the third man that she was married to.
7.He chosed the fourth picture.
8.We are to carry out the first plan．
9.I am the first in our class.
10.We'll go over it a second time．
11.We've tried it three times．Must we try it a fourth time?
12.Mother was my first teacher in my life.
13.One fifth of the students here are from the country.
14.Please give me a second chance.
15.She stands first in her class.
16.Tom is Lily's third boyfriend.
17.Now,what should I do first?
18.The poor woman had a third baby.
19.He was born at the first sunday of May.
20.This is Lily's first time to eat shit.