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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

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 _______ nothing can be done to change it.

A. begins B. having begun  C. 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

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

A. begins B. having begun

C. beginning   D. begun