题目内容：

All the tasks _______ahead of time ,they decided to go on holiday for a week.
ll the tasks _______ahead of time ,they decided to go on holiday for a week.
A had been filled B having been filled
C were filled D been filled
All the tasks _______ahead of time ,they decided to go on holiday for a week
A had been filled B having been filled
C were filled D been filled

优质解答

B having been filled
逗号后面是一个完整的句子,又没有and连接,所以,前面的句子,不应该是一个完整的句子,其他选项放进去,都是一个完整的句子,也就是说,had,were都可以做谓语动词.
D的话,没有have提示,怎么能用been呢,been是过去分词,和have一起,才能表示完成时的,不能单独用
此处是现在分词的完成时作原因状语,相当于原因状语从句,可用because,since,for来改写.