摘要： The research is so designed that once nothing can be done to change it.A. begins B. having begunC. beginning D. begun[解析] D.由于 the research 与 begin 是被动关系.故用过去分词 begun.Once begun 可视为 once it is begun 之省略.
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The research is so designed that once _______ nothing can be done to change it.
A. begins B. having begun
C. beginning D. begun
查看习题详情和答案>>The research is so designed that once ____ nothing can be done to change it.
A. begins B. having begun C. beginning D. begun
查看习题详情和答案>>The research is so designed that once _______ nothing can be done to change it.
A. begins B. having begun C. beginning D. begun
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