21岁英语怎么说

twenty-one years oldtwenty-one-year 都是21岁的,但前面year加s ,后面的不加

years---old

twenty-one years old twenty-one-year-old

twenty-one years old

twenty-one year oldor twenty one years old

直接说twenty-one 或者 twenty-one years old或者 at the age of twenty-one

英文 21岁 怎么说twenty-one years old21 years oldThe boy is 21 years old.