— Who are those people gathering in front of the building? — A group itself the youth vol

问题补充：

— Who are those people gathering in front of the building?

— A group itself the youth volunteers.

A. calling

B. calls

C. called

D. to be called

答案：

A. calling

B. calls

C. called

D. to be called

解析：考查分词做定语。本题的动词call与a group构成主动关系，故使用现在分词的形式。句意：—聚集在大楼前面的那些人是谁啊？—一一群自称为青年自愿者的人。故A正确。