68. A new technique ______ , the yields as a whole increased by 20 per cent.　　　　 A)working out 　　　　 B) having worked out 　　　　 C)having been worked out 　　　　 D)to have been worked out

熱心網友

A 這是語感 念書多了就有這種感覺 抱歉 具體的我不是很清楚 不過我敢肯定就是這個答案

熱心網友

agree