The research is so designed that once nothing can be done to change it. A．begins

    once(或者其他连词如when，while，since等)引导状语从句时，如果从句主语与主句主语一致，可以省略其中的主语和be动词谓语结构，例如：

    Once inbed, the children usually stay there.

    (=Oncethey are in bed, the children usually stay there.)

    Whenfinished, the building will be opened by the Prince of Wales.

    (=Whenit is finished, the building will be opened by the Prince of Wales.)

    While atcollege (=While she was at college), Delia wrote a novel.

    本题所给句子的句意为：

    Theresearch is so designed that once it (=the research)is begun nothing can bedone to change it．也就是：

    ...once begun nothing can be done to change it．