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题目内容
（安徽理工大学-电气工程及其自动化）
The millions of circulations involved, _____ by hand, would have lost all practical value by the time they were finished.
A、had they been done
B、they had been done
C、having been done
D、they were done
A、had they been done
B、they had been done
C、having been done
D、they were done
参考答案