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题目内容
（宿州学院大学英语2）
5
The research is so designed that once ______nothing can be done to change it.
A、
begins
B、
having begun
C、
beginning
D、
begun
参考答案
5
The research is so designed that once ______nothing can be done to change it.
A、
begins
B、
having begun
C、
beginning
D、
begun