问题补充:
--- Do you know the boy is sitting next to Peter?
--- Yes. He is Peter’s friend. They are celebrating his birthday.
A. who; ninth
B. that; nineth
C. /; nineth
D. which; ninth
答案:
(答案→)A. who; ninth
B. that; nineth
C. /; nineth
D. which; ninth
解析:句意:---你知道正挨着Peter 坐的那个男孩吗?---是的,他是Peter的朋友,他们正在庆祝他的第九个生日。定语从句中先行词是人用who, that都可以,因为关系词在句中作主语所以不能省略,某人的第几个生日用序数词,nine的序数词为ninth故选A。