He is the only one of the student in our school _____ the paino well.为什么不能用that play 要用who play.不是the only修饰必须that么

是the only one of the students,别忘记有students在这里.in our school 是定语,修饰前面的only one of the students.这是一个定语从句,先行词是the only one of the students,是人,而且play the paino well前面缺主...