Without facts,we cannot form a worthwhile opinion for we need to have factual knowledge __________ our thinking.

Without facts,we cannot form a worthwhile opinion for we need to have factual knowledge __________ our thinking.
A.upon which to base B.which to be based on
C.which to base upon D.to which to be based
______________ that they may eventually reduce the amount of labor needed on construction sites by 90 percent.
A.Such construction robots are clever
B.So clever the construction robots are
C.So clever are the construction robots
D.Such clever construction robots are
All flights__________ because of the storm,they decided to take the train.
A.having canceled B.were canceled
C.have been canceled D.having been canceled
区分 guilt charge blame accusation 这四个词各自是用在什么场合?