Do you know the boy is sitting next to Jim? Yes. He is Jim’s friend. They are celebrating

Do you know the boy is sitting next to Jim?
Yes. He is Jim’s friend. They are celebrating his birthday.
A. who, ninth
B. that, nineth
C. /, nine
D. which, nine

(答案→)A. who, ninthB. that, ninethC. /, nineD. which, nine解析：此题重点考查定语从句的引导词和序数词的用法。先行词The boy 在从句中充当主语，引导词可以用who也可用that。某人的第几生日要用序数词。

感谢回答，我学习了