题目内容
All that can be done ________ done.A. has been
B. have been
C. has
D. have
答案：A
解析：
提示：
解析：
| 主语从句看作单数。
|
提示：
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题目内容
All that can be done ________ done.A. has been
B. have been
C. has
D. have
| 主语从句看作单数。
|