问题补充：
The Diaoyu Islands have been part of China’s territory since ancient times, as important fishing grounds of Taiwan.
A. served
B. to serve
C. serving
D. having served
答案：
A. served
B. to serve
(答案→)C. serving
D. having served
解析：考查现在分词做状语：句意：钓鱼岛自从中国古代就是中国的领土，做为台湾重要的渔业基地。The Diaoyu Islands和serve as是主动关系，用现在分词做状语，选C.
