Question

--- 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

Answer 1

A

修饰名词boy是一个定语从句，先行词是人，所以关系词是who，九的序数词为ninth，故本题选A。