问题补充:
The singer sang one more song at the of enthusiastic fans.
A. command
B. recognition
C. request
D. service
答案:
A. command
B. recognition
(答案→)C. request
D. service
解析:at the request of sb 在某人的要求下 A. command“命令”;B. recognition“认知”;D. service“服务”,所以答案为C