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

68. A new technique __C)having been worked out ____ , the yields as a whole increased by 20 per cent.　　　　 A)working out 　　　　 B) having worked out 　　　　 　　　　 D)to have been worked out technique 做邏輯主語， 應該用完成被動式，

熱心網友

I agree with the second answer.

熱心網友

本人認為選B。新的技術產生作用之后，產量上升了20%。新技術的作用當然是已經產生，而且正在產生，所以用現在完成進行時。