The research is so designed that once (begun) nothing can be done to change it.括号里的词为什么...The research is so designed that once (begun) nothing can be done to change it.括号里的词为什么用过去分词?

The research is so designed that once ___ nothing can be done to change it.A.begins B.having begun C.beginning D.begun(答案是D,为什么?) The research is so designed that once ____ nothingcan be done to change it.A.begins B.havingbegun C.beginning D.begun要怎么选 The research is so designed that once _______ nothing can be done to change it.A.begins B.having begunC.beginning D.begun The research is so designed that once _______nothing can be done to change it.A. begins B. having begun C. beginning D. begun求详解.waiting Eg:The research is so designed that once_____ nothing can be done to change it.A begins Bhaving begun C begining D begun.Why choose The research is so designed that once ________ nothing can be done to change it.A.begins B.having begun C.beginning D.begun The research is so designed that once begun nothing can be done to change The research is so ------- that it leaves no part of the issue unexamined.comprehensiverewardingsporadiceconomicalproblematical 应该选择哪个 15、he_____himself with video games,so he had no time________A、 enjoyed B、 hurt C、 busied D、bought16、__we have to admit that man’s research into space is still in the ____________A、 initial B、childish C、 endless D、subjective The research is so designed that once ___（begin ）nothing can be done to change it 正确形式填空 一段英文求高手帮忙翻译谢谢~Pharmaceutical companies are focused on getting new targeted therapies approved and marketed as quickly as possible. And the pace of research surrounding these drugs is staggering. There are so many exciting d 求助一道非谓语动词的选择题The research is so designed that once _____ nothing can be done to change it .A.begins B .having begun C.beginning D.begun我认为应该选C,因为从“研究开始”这种说法来看research和begin应该 英语翻译There has been considerable debate over the last decade or so on the effectiveness of construction project planning.However,there is remarkably little research into what construction project planners actually do.The research reported here 英语翻译There has been considerable debate over the last decade or so on the effectiveness of construction project planning.However,there is remarkably little research into what construction project planners actually do.The research reported here Is this the research center____the foreigners visited last week?A; what B; which C; where D;the one is this research center ___ the guests visited yesterday.A that B which C where D the one 1、John said he'd been working in the office for an hour,＿was true.A、he B、this C、which D、who2、＿in thought,he sat still in the sofa.A、losing B、having lost C、lost D、to lose3、The research is so designed that once＿nothing can b Science, so the story goes, is a meticulously built edifice. Discoveries balance on ones that prece请大侠翻译.Science, so the story goes, is a meticulously built edifice. Discoveries balance on ones that preceded them. Research is stimulated by