Bill is ten years old.He has a _______sister

问题描述:

Bill is ten years old.He has a _______sister
A 4 years old B 4-year-old 这两个选项都对,要选哪个?

Bill is ten years old.He has a _______sister
A 4 years old B 4-year-old
选B 只有选项B 4-year-old 才能做定语,修饰 sister