China's sport stars Yao Ming and Liu Xiang _________ Goodwill Ambassadors (亲善大使) for            Shanghai.      [ ]

A. has been named

B. have been named

C. has named

D. have named

6月6日，为全国“爱眼日”，今年的主题是，“预防近视，珍爱光明”，图中表示某两人看物体时的光路图，要在视网膜上成清晰的像。甲须配戴          镜，乙须配戴          镜。