In the sentence "
All the tasks having been fulfilled ahead of time
, they decided to go on holiday for a week", the underlined phrase is _____.
【正确答案】
A
【答案解析】解析：all the tasks having been fulfilled ahead of time属于独立主格结构，在句中充当原因状语。可还原为As all the tasks have been fulfilled ahead of time。故答案为A。