Do you know the girl is singing in the classroom?A. whoB. whichC. whenD. that

问题补充：

Do you know the girl is singing in the classroom?

A. who

B. which

C. when

D. that

答案：

(答案→)A. who

B. which

C. when

D. that

解析：句意：你认识这个正在教室里面唱歌的女孩吗？结合语境可知本句中先行词the girl为下文定语从句中的逻辑主语，指人，故引导词用who，选A。