.----Who are those people gathering in front of the building?---A group itself the you

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：

(答案→)A. calling

B. calls

C. called

D. to be called

解析：考查现在分词做定语，句意：--在大楼前聚集的人是谁？--一群自称为青年自愿者的人。说明这个空填定语，A group和call itself是主动关系，用现在分词做定语。选A。