A new technique ____ out, the yields (收成) increased by 20% .
A.having working
B.having been working
C.has worked
D.had been worked
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B解析 根据逗号分开可知空白处不能填入谓语动词，A项从形式上就不对，根据语境应该用现在分词的完成式，此处work out表示“产生结果；有预期的结果，发展为”例如:I wonder how their ideas worked out in practice?我很想知道他们的想法在实践中取得了什么结果。