问题
The research is so designed that once ______ nothing can be done to change it[ ]
A: begins
B: having begun
C: beginning
D: begun
B: having begun
C: beginning
D: begun
正确答案是：
同类题型
almost ___________ laughing when I saw what she was wearing. [ ]
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Would you please _________ me of the meeting tomorrow morning. ——- Don’t worry. I _________ .