问题补充：
My friend, who on the International Olympic Committee all his life, is retiring next month.
A. served
B. is serving
C. had served
D. has served
答案：
A. served
B. is serving
C. had served
(答案→)D. has served
解析：考查时态题。句意：我的一个朋友已经为国际奥委会工作了一辈子，他下个月就要退休了。指他已经为奥委会服务了一辈子了，使用现在完成时表示动作持续到现在。故D正确。
