China's sports start Yao Ming and Liu Xiang ___ Goodwill Ambassadors for Shanghai.
问题描述：
China's sports start Yao Ming and Liu Xiang ___ Goodwill Ambassadors for Shanghai.
A has been named B have been named C has named D have named
选哪个为什么,谢谢,顺道翻译
答
B
中国运动明星姚明和刘翔被认为是上海的慈善大使