All the task ahead of time, so they decided to go on holiday for a week.
A. having finished
B. had finished
C. having been finished
D. had been finished
网友回答
A. having finished
B. had finished
C. having been finished
(答案→)D. had been finished
解析：这题考查句式，so引导的是结果状语从句，所以前面是主句，应该填谓语动词，时间是发生在they decided to go on holiday for a week.之前，而且task和finish是被动关系，用过去完成时的被动式，选D。