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

问题补充：

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：

A. begins

B. having begun

C. beginning

(答案→)D. begun

解析：此题也为省略句。连词once后省略了主语the search，从句“once begun”相当于“once the search is begun”。答案为D。