—Do you know the boyis sitting next tu Peter?--Yes he is Peter’s friend.They are celebrat

问题补充：

—Do you know the boyis sitting next tu Peter?

--Yes, he is Peter’s friend.They are celebrating hisbirthday.

A. who;ninth

B. who; nineth

C. that;nineth

D. which;ninth

答案：

(答案→)A. who;ninth

B. who; nineth

C. that;nineth

D. which;ninth

解析：定语从句用来充当句中定语的成分，被修饰的名词叫先行词，连接主从句的是关系词。关系词分：1关系代词：who , whom , whose , which , that。2关系副词：where,when why 等。一般的who 用于指代人的先行词，which 用来指代物的先行词，that既可指认又可指物。关系代词在从句中作主语、宾语。该句先行词是人，故用who 引导，第九，去e加th,故选A