请帮忙选一下,并说明理由,谢谢

　　　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

热心网友

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 做逻辑主语， 应该用完成被动式，

热心网友

I agree with the second answer.

热心网友

本人认为选B。新的技术产生作用之后，产量上升了20%。新技术的作用当然是已经产生，而且正在产生，所以用现在完成进行时。