独立主格结构什么时候用完成时?

Question

独立主格结构什么时候用完成时?
如这个题：
All flights ______ because of the snowstorm, many passengers could do nothing but take the train.
A）had been canceled B）have been canceled
C）were canceled D）having been canceled
因为风雪，所有航班都被取消，许多旅客别无它法，只得乘火车。(D)

All things ______, the planned trip will have to be called off.
A）considered B）be considered
C）considering D）having considered
考虑了方方面面之后，原来计划好的旅行不得不取消了。(A）
为什么前者要用完成时而后者不用？

Answer 1

第一，当从句的谓语发生的动作给主句造成一定的影响，有了一个结果。如：第一道题可改写成：Many passengers could do nothing but take the train because all flights has been canceled.
第二，当从句的动作先于主句的发生，就要用到having done/having been done.

在第二道题中,all things跟consider是动宾关系（被动），而不存在第一题里的关系。所以不用完成时。