题目内容:
A new technique( ),the yields as a whole increased by 20 percent.
A.working out
B.having worked out
C.having been worked out
D.to have been worked out
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答案解析:
A new technique( ),the yields as a whole increased by 20 percent.
A.working out
B.having worked out
C.having been worked out
D.to have been worked out