At the root of volunteering is idea that one person may have ability to offer services tha

问题补充：

At the root of volunteering is idea that one person may have ability to offer services that can help other people.

A. the, the

B. 不填; an

C. an ; 不填

D. 不填，the

答案：

(答案→)A. the, the

B. 不填; an

C. an ; 不填

D. 不填，the

解析：考查冠词：句意：志愿者的根源是一种想法，一个人可能有能力提供帮助别人的服务。第一空填the，是特指某种想法，第二空填the，特指提供别人帮助的能力，选A。