问题补充：
All that can be eaten eaten up.
A. are being
B. has been
C. had been
D. have been
答案：
A. are being
(答案→)B. has been
C. had been
D. have been
解析：选择B。本题题干中than can be eaten是定语从句，其所修是的先行词是all，那么就是说all 才是真正的主语，根据句意是说：所有能吃的都被吃光了。“食物”作主语，应当是单数谓语动词才是，所以选择B。
